Anas رضي الله عنه narrated that Allah's messenger 
said..
"All the sons of Adam are sinners, but the best of sinners are those who repent often"
(Tirmidhi and Ibn Maajah)
Lessons to be learnt:
-The human being in general is limited in his abilities regardless of how much Taqwaa (fear of Allah) he has
-Human beings are different in their ranks concerning their obedience and disobedience to Allah سبحانه وتعالى
-It is necessary for the Muslims to quit evil doing and to hasten to repentance
-Allah's mercy is so great
-Repentance from all sins is a must
-A Muslim should not give up hope at any time on Allah's mercy and forgiveness
-A Muslim should repeat his Tawbah, i.e. his repentance at any time and everytime he does something wrong.
