It is easy to be guilt ridden and get into a self-destructive path. Even the idea & thought is as dangerous as the action itself. All I can say is that it is important for you to let go of the past. Our mind has a unique good & evil counter to ensure a balance. After every incident of evil or action that we are ashamed of, we try to commit a good to balance it out. Similarly after every good achievement, we like to treat our senses with an indulgence.
Most people go for the amnesia pill/drugs/alcohol; they remove all traces and forget it ever happened. Guilt is a monster that one can sweep below the rug but its ugly head will sabotage you in the future. Denying the existence only makes the demon stronger. Some people become religious & penance to cleanse themselves. In fact the purpose of religion is to give us mere mortal a tool to get rid of the clutter in our conscience and justify/rationalize some of our actions. Some people look for a distraction to keep them occupied and prevent their minds going astray. Some go for confession to come clean. I have known people going for kids and bury themselves with additional responsibilities so that there is no free time to morn. Others make sacrifices or give generous donations to cleanse their souls.
One is free to choose the coping mechanism that works for them as long they have been able to let go. I have seen relationships actually strengthen after an incident. People become more mature, take responsibility for their action. You can become more focused and if channelized properly you can use that past incident to get rid of whatever baggage you want to shed.
One unhealthy way is to rationalize their actions. It could be as simple as saying, “yeh to sab karte hai!” (everybody does that), or cite the celebrity/much revered person. Sometimes we rationalize our situation, often creating semi-fictitious restriction/problems/situations/dilemma which over-exaggerates the pros-cons of the options we had and try to get a moral sympathy. It is equivalent to create an external locus of control, where we are trying to justify our existence as mere puppets whose hands were tied. The worst kind of rationalization is to deny the victim claim to be human and finding flaws in the victims. Slave owners could preach religion & morality while beating & burning their slaves because they felt the blacks were nothing more than livestock. Terrorist believe their victims are infidels and hence cannot be judged with the same sense of morality.
The problem with these methods is that they tend to change one’s perception of the world, and hence alter the character towards the dark side. Many of these rationalizations are irreversible and they lower our standards for morality. A girl might think a thousand times before her first time, but after that the next thousand times happen without batting an eye lid. Anybody can brainwash themselves or find a book/leader that could do it for you. The question is it what you want?
The way I see it, everyone has three choices, a) they can continue to be tormented by the demons of their past; b) accept them and work towards making amends and moving on; or c) drift towards the dark side by rationalize the past and making friends with these demons.