How can one repent to Allah and rid oneself of sins, despite repeatedly returning to them and feeling despair, loss of reverence, and lack of self-confidence?

The door of repentance is open and will not close until the sun rises from the west. The mercy of Allah is wider than any sin. Allah Almighty says: "And it is He who accepts repentance from His servants and pardons evil deeds and knows what you do," and He says: "Say, 'O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful.'" To repent from sins, seek help from Allah, supplicate persistently, strive against your lower self, remember the consequences of sins, keep company with the righteous, increase in acts of obedience, listen to beneficial admonitions, ponder over death, and be mindful that Allah is watching you.