I feel guilty each I remember the mistake I made

It was four years ago when I met this guy in a friend’s party and we spent several hours of kissing before we parted. It was just a drunk night out with a friend.

Later on, I found out that he was the son of one of my father’s friends. My younger sister (20 years of age at the time) and him met and fell in love and became boyfriend/girlfriend.

Right after they started being together, I drove with him into town to meet a friend and I got pretty drunk. On the way back, he pulled in and started kissing me.

Nothing else happened, as we drove home and agreed to never tell anyone, since we were drunk and it didn’t mean anything.

After a month, we were sitting together and talking and got drunk again. We ended up in bed together and did it again a week or so later. Later on, he tried to kiss me, but I pushed him away.

The problem now is that the thought of it is killing me. I love my sister more than anything else in this world.

If she would ever stop existing, I would too. I would die for her. And if I could, I would give my whole life to go back in time and undo it.

Their relationship lasted only a few months. I told her last year that we had kissed and she didn’t get angry at me at all. I couldn’t tell the whole story. I am scared deep within my soul that she will never forgive me or never trust me again.

I know that is the least I deserve, but I just can’t. I will never be able to see myself as a good person again, but I need to do something, so I can function again. What should I do?