Regret

At some point in your life you will do something you regret doing later, only the magnitude of the mistake is the question. After you've done something you regret and come to the place where you realize it was a mistake one of two things will happen: you will either emerge from the pain a better person or drown in self-pity and self-loathing. The pain of realizing a big mistake encompasses you in a darkness that is indescribable, only those that have been there can relate. You must walk towards Christ's healing power, or forever stay in the darkness - and endlessly try and drown out the pain using other methods.

From personal experience, there are multiple steps you go through on your way to healing. First, there's the realization that you made a mistake. This first step can definitely be the hardest to get past, because our human nature wants to deny that we ever made a mistake. To drown out the negative chorus we will usually do the exact same thing, or try and get others to follow our footsteps so that we don't feel as bad about our own errors.

The second step to recovery, once you have decided to right your wrong, is forgiveness of self. You do not deny that what you did is wrong, you do not minimize the pain you caused yourself and you do not forget your error. You forgive yourself. You must forgive your own ignorance, your own stupidity, your own weaknesses, and whatever else caused you to fall in this pit.

Lastly, you need to mend the wounds you've caused, to yourself and others. Some mistakes will stay with you for life. Ask the murderer spending the rest of his life in jail or the adulterer who will never see his bride again - they may have forgiven themselves but their punishment is lifelong.

2 Corinthians 7:10
"Godly sorrow brings repentance that leads to salvation and leaves no regret, but worldly sorrow brings death."