True meaning of istighfār in Islam

Nahj al-Balāgha|Volume 1|Book 3|Chapter 417

Book 3, Chapter 417

وَالثَّانِي: الْعَزْمُ عَلَى تَرْكِ الْعَوْدِ إِلَيْهِ أَبَداً.

the second is to make a firm determination never to revert to it;