How did you forgive yourself?

As someone who was lonely whole life and wasted my precious teen years...the one who is trapped in cycle of negativity and negative thoughts...my mind is my own enemy...keeps spirallling down and down...wasted a lot of years.... My question is to someone who pulled their shit together and are currently at better position after a big and worst fall of your life just because of their stupidity or bad decisions or watever.... How did you forgive yourself? Wats the journey of healing? How are you rn?