If one is unable to follow a regulative principle after many years of chanting, should one give up chanting due to guilt and shame?

From: Rajesh :

What if one is not able to follow the last regulative principle even after chanting for 8 years, should that person give up chanting and devotional service because there is guilt and shame for past conditioning of lust?

An important verse quoted in the answer:

jata-shraddho mat-kathasu  nirvinnah sarva-karmasu

veda duhkhatmakan kaman parityage ‘py anishvarah

tato bhajeta mam pritah shraddhalur dridha-nishcayah

jushamanash ca tan kaman duhkhodarkamsh ca garhayan

Having awakened faith in the narrations of My glories, being disgusted with all material activities, knowing that all sense gratification leads to misery, but still being unable to renounce all sense enjoyment, My devotee should remain happy and worship Me with great faith and conviction. Even though he is sometimes engaged in sense enjoyment, My devotee knows that all sense gratification leads to a miserable result, and he sincerely repents such activities. (SB 11.20.27-28)