Everyone makes bad decisions sometimes. Unless of course one is perfect, and even saints make mistakes before they become realized. Once you make a mistake it cannot be undone. To not admit a mistake only makes it easier to repeat. Repeating mistakes only makes eventual self-punishment worse.
The mind is a funny thing. It can tell you, "It's alright. No one will find out, no one will get hurt." But in the meantime, what happens to you? Are you still able to feel the same way about yourself? Do you find yourself having to hide things for people you care about? Do you live with the fear of being found out?
Since mistakes are inevitable, it is usually best to find someone to whom you can trust to listen to you. They must also be someone you can trust not to gossip. Try to sort out with this confidant how to resolve your mistake. You might be surprised that what you have done is not as bad as you think. Or maybe it is as bad as you think - maybe you are guilty of hurting a person who is innocent.
By talking to someone you can begin to resolve how you feel and if it is appropriate make amends to the person or people your mistake affected. The main thing is, by not keeping your secret to yourself you take responsibility for yourself so you can move on.
You are a victim of your own bad decisions when you don’t deal with them. If you treat yourself with enough kindness and firmness there is a good chance that you will be able to resolve your mistake with the least amount of hurt involved for everyone.