Shaykh Muhammad Saleem Dhorat explains that Imaan is our greatest wealth and Shaytaan and nafs are our greatest enemy who are able to snatch it away from us. The means of safeguarding this great wealth of Imaan is adopting Taqwa, i.e. to abstain from sins and to fear the displeasure of Allah (subhanahu wa ta'ala)
To be able to adopt Taqwa we should stay with the Saadiqeen (the Truthful). Spending time with the Truthful will lead to the realisation that we have the ability to abstain from disobedience because a great deception of Shaytaan is to make us concentrate on our good deeds. We concentrate on our worship, spending our time and wealth in the path of Allah, our optional hajj and umrah etc. not that there is no benefit in our optional worship. There is definitely benefit in this however the benefit is insignificant compared to the detrimental effect of committing sins.
Therefore the key to the security of Imaan is adopting Taqwa and the key to adopting Taqwa is to be with the Saadiqeen (to spend time with and to consult a Shaykh).