Ignorance is the root cause of sinful life. If we pull up weeds from the garden but do not get the root, then the plant will grow back. If we do not remove the root of ignorance from our heart, then the sinful desires will grow back. Prahlada Maharaja prays, "Please appear in our hearts and drive away our ignorance so that by Your mercy we may become fearless in the struggle for existence in this material world." This is the only way to become fearless; ignorance must be completely driven out by the Lord's mercy. Krishna, who is situated within the heart, destroys material desires in the core of the heart of that person who develops the desire to hear about His transcedental pastimes.
Lectures from a disciple Vol 1, attachments and material desire, Pg 467-468 last paragraph