الجواب وباللہ التوفیق

Assalamualaikum Warahmatullah

Regardless of the type of sin, the method to repent for a sin is to perform tawbah and tawbah is the kaffarah for the sin as well. Therefore one should perform tawbah with sincerity and remorse upon their sin(s) and make firm intention not to repeat it. In addition, one should not wait or get worried about attaining firm belief that they have been forgiven. However one should make tawbah with the hope that it will be accepted and keep fear of it not getting accepted as well. When someone performs tawbah, dua and other Islamic duties with the concept of hope and fear, it leads to achieving the true soul and essence of Islam. It has been mentioned in a hadith of Rasulullah Sallallaho Alyhi Wasallam:

الایمان بین الخوف والرجاء

Translation: Iman should be constituted of both hope and fear.

When you will perform tawbah and other Islamic duties with clarity and sincerity of your heart then InshahAllah, Allah Subhanahu Wa Ta‘ala will also bestow the treasure of serenity and peace upon you.

فقط واللہ اعلم