What one receives from the Qur'aan, how much one understands of the Qur'aan and how much one is truly guided by the Qur'aan is not a static process. It is indeed a dynamic process that is directly related to one's faith and willingness to apply the Qur'aan. As the person learns and applies the Qur'aan, his understanding of the Qur'aan increases even further. The one whose heart already has faith and a willingness to submit to and apply the Qur'aan is the one who really learns the Qur'aan. This was the case with the Companions رضي الله عنهم of the Prophet صلى الله عليه وسلم.
Indeed, Allaah سبحانه و تعالى calls the Qur'aan a guidance for those who are God-fearing and apply Islaam: "This is the Book, in it is guidance sure, without doubt, for those who fear Allaah; who believe in the Unseen, are steadfast in prayer, and spend out of what We have provided for them. And who believe in the revelation sent to you and sent before your time, and (in their hearts) have the assurance of the Hereafter. They are on true guidance from their Lord and it is these who will prosper."
(Sooratul Baqarah, 2:2-5)
Commenting on these verses, Sayyid Abul A'laa Maudoodi رحمه الله wrote,
"This means that while the Book is potentially for all, only those who possess certain qualities can benefit from it. The first such quality is piety: those who want to benefit should be disposed to distinguish between good and evil, and to shun evil and do good. Those who lead an animal existence, who never stop to consider whether their actions are either good or bad, who cynically follow the prevailing winds, who are helplessly tossed about by the animal desires that dominate their minds, such persons are altogether incapable of deriving any benefit from the guidance embodied in the Qur'aan." 
If someone's heart is filled with pride, arrogance, vanity or other diseases or if a person's only concern is to satisfy his whims and desires, and he has the least desire to change his way of life according to the Qur'aan, he may get nothing from his reading of the Qur'aan. If, on the other hand, he does have some desire to mend his ways and live a goodly life, then each time he reads and applies the Qur'aan, his understanding and application of the Qur'aan will improve. Finally, the diseases in his heart will be removed and he will become one of the pious. And if a person whose heart and actions are pure and righteous turns to the Qur'aan, his heart and mind will be completely attuned to it and he will be granted guidance upon the guidance that he already possessed. "And those who strive in Our (Cause), We will certainly guide them to Our paths: for verily Allaah is with those who do right."
(Sooratul 'Ankaboot, 29:69) "For believers are those who, when Allaah is mentioned, feel a tremor in their hearts, and when they hear His revelations recited, find their faith strengthened, and put all their trust in their Lord."
(Sooratul An'aam, 8:2) "But those who believe and work deeds of righteousness and believe in the (revelation) sent down to Muhammad for it is the truth from their Lord, He will remove from them their sins and improve their condition."
(Soorah Muhammad, 47:2)
Sayyid Qutb رحمه الله convincingly argues that unless one applies the Qur'aan in his actions and actually begins to live in its shade, he will never really taste the sweetness and experience the guidance of the Qur'aan. In one passage, he states, "The underlying lessons of this Qur'aan will never be revealed to those who simply sit, those who discuss its texts in light of its linguistic and rhetorical principles ... They are the ones who simply sit." 
The teachings and guidance of the Qur'aan are meant to be lived and applied to reality; as long as the person does not attempt to live and apply them, there will always be a barrier between him and the essence of the Qur'aan. Sayyid Qutb رحمه الله emphatically notes,
"The [sweet taste] of this Qur'aan is not to be tasted save by the one who dives into the struggle. The one who faces the same situations concerning which it was revealed and faces them in the same way [that the Qur'aan] faces them. Those who search for the meaning and evidences of the Qur'aan while they are sitting studying it as speech or art only will never be able to discover the reality of the Qur'aan from that motionless, barren sitting far away from the struggle and far away from the movement. The reality of the Qur'aan is never revealed to those who simply sit. Its inner truth will never expose itself to those who are overtaken by rest and relaxation while they serve other than Allaah سبحانه و تعالى or submit to false lords and not to Allaah." 
Sayyid Abul A'laa Maudoodi رحمه الله eloquently echoed the same thoughts when he wrote,
"It should be remembered, nevertheless, that full appreciation of the spirit of the Qur'aan demands practical involvement with the struggle to fulfil its mission. The Qur'aan is neither a book of abstract theories and cold doctrines which the reader can grasp while seated in a cozy armchair, nor is it merely a religious book like other religious books, the secrets of which can be grasped in seminaries and oratories ....
This is the Book which inspired and directed that great movement which began with the preaching of a message by an individual, and continued for no fewer than twenty-three years, until the Kingdom of God was truly established on earth. In this long and heart-rending struggle between Truth and falsehood, this Book unfailingly guided its followers to the eradication of the latter and the consolidation and enthronement of the former. How then could one expect to get to the heart of the Quranic truths merely by reciting its verses, without so much as stepping upon the field of battle between faith and unbelief, between Islam and Ignorance? To appreciate the Qur'aan fully one must take it up and launch into the task of calling people to God, making it one's guide at every stage.
Then, and only then, does one meet the various experiences encountered at the time of its revelation ...
Again, in keeping with the same principle, a man can neither understand the laws, the moral teachings, and the economic and political principles which the Qur'aan embodies, nor appreciate the full import of the Quranic laws and regulation, unless he tries to implement them in his own life. Hence the individual who fails to translate the Quranic precepts into personal practice will fail to understand the Book." 
Furthermore, this Qur'aan - this light from Allaah سبحانه و تعالى - is something special. The one who has been blessed by Allaah سبحانه و تعالى to receive it must realize that he has been given something special by Allaah. 
Therefore, the behavior of that person must be a dignified one, corresponding to the dignified bounty that he has received. The Companion Abdullaah ibn 'Amr رضي الله عنهما said, "The one who has memorized the Qur'aan is carrying with him a great matter. The level of prophethood is in him except that he does not receive revelation. Therefore, the one who knows the Qur'aan must not get angry in circumstances where the others get angry nor should he indignant when the others become indignant for in his heart is the Qur'aan." 
Finally, one should realize that there is a relationship between committing sins, in other words, not living by the Qur'aan or in its shade, and loss of knowledge. Shaykh Naasir al-'Umar حفظه الله stated,
"[Committing sins is] the worst of the things that destroys knowledge. It crushes knowledge as a fire devours branches. How many forbidden looks led to the loss of a great deal of knowledge. Or [how often has] a small amount of forbidden or doubtful wealth turned knowledge into a mirage ... Verily Allaah سبحانه و تعالى has stated the truth [when he said], 'Those truly fear Allah among His servants who have knowledge.'"
(Soorah Faatir, 35:28) 
Hence, the more one commits sins, the farther he strays from the Qur'aan and the more and more difficult it becomes for him to see, understand and apply the guidance of the Qur'aan.
In addition, sins and disobedience to Allaah سبحانه و تعالى can lead to one's heart being hardened. One's heart can become blinded and sealed. This is one of the greatest blockades to getting the guidance from the Qur'aan. As Allaah سبحانه و تعالى says in the Qur'aan, "Do they not ponder over the Qur'aan or are their hearts sealed?"
(Soorah Muhammad, 47:24)
When the heart is sealed, the light of the Qur'aan - by Allaah's will and command سبحانه و تعالى - is not able to penetrate it.
Khurram Murad's رحمه الله comments on this topic are a good conclusion concerning this matter. He wrote,
"Unless you are prepared and begin to act to shape your thoughts and actions according to the messages you receive from the Qur'aan, all your dedication and labour may be to no avail. Mere intellectual exercises and ecstatic experiences will never bring you anywhere near the real treasures of the Qur'aan."   Notes:
 Sayyid Abul Ala Maududi رحمه الله, Towards Understanding the Quran (Leicester: the Islamic Foundation, 1988), vol. 1, p. 45, fn. 3. In the following footnotes Sayyid Abul A'laa Maudoodi رحمه الله discusses the other prerequisites, mentioned in the above verses, of belief in the unseen, establishment of the prayer, giving charitably from one's wealth, belief in the books revealed and belief in the unseen.
 Sayyid Qutb رحمه الله, Fee Dhilaal al-Qur'aan (Cairo: Dar ash-Shuruq, 1992), vol. 3, p. 1453.
 Ibid., vol. 4, p. 1865.
 Sayyid Abul Ala Maududi رحمه الله, An Introduction to Understanding the Quran (Riyadh: WAMY, 1990), pp. 36-39.
 All Muslims must feel this way with respect to their bounty of being guided to Islaam. They must realize that Allaah سبحانه و تعالى has given them something special and, in return, they should behave properly with respect to that special bounty that Allaah سبحانه و تعالى has given them.
 Quoted in Imaam Abu Bakr al-Aajuri رحمه الله, Akhlaaq al-Qur'aan (Beirut: Daar al-Kutub al-'Ilmiyyah, 1987), pp. 55-56. Its chain is sound.
 Shaykh Naasir al-'Umar حفظه الله, Al-'Iim: Daaroorah Shar'iyyah (Riyadh: Daar al-Watn, 1412 A.H.), p.
64. Also see Shaykh Bakr Abu Zaid رحمه الله, Hilyah Talib al-'Ilm (Cairo: Maktaba al-Tauiya al-lslaarniyyah, 1989), p. 9.
 Khurram Murad رحمه الله, Way to the Quran (Leicester, UK: The Islamic Foundation, 1985), p. 33.
 Taken from: Shaykh Jamaaluddeen Zarabozo حفظه الله, How to Approach and Understand the Quran (Boulder, CO, USA: Al-Basheer Company for Publications and Translations, 1999), pp. 178-184