One of the most powerful ways to cleanse one’s heart is isolation even for 5 minutes a day, as the Prophet (saw) would go to Mount Hira and sit and contemplate for hours and days at end and this was when he was married with 6 children!
Sit alone and think of all the sins you have done and repent and cry and do this regularly. A scholar of the past would say it’s good to repent even from the makruh actions and actions which are recommended but you left for some reason. SubhanAllah! So what about the big sins we commit!!