Everyone makes bad decisions - unless of course you are perfect. Mistakes made cannot be unmade However, harm done can almost always be mitigated and the results can help fertilize your soul. On the other hand, when a mistake is denied or continues to be repeated, can become a recipe for eventual disaster.
The mind is a funny thing. It can say "It's alright. No one will find out, no one will get hurt." But in the meantime, what happens to you? Are you still at peace with yourself? Do you find yourself distancing from people you care about, or worrying about being found out?
Since mistakes are inevitable, admitting them as soon as you can and making amends is often the best course of action. However, if a mistake is big enough and serious enough, you may first need to find someone that you can trust to talk to about it. Otherwise, you will be left listening to the distorted advice of your own troubled mind.
Most people who make mistakes overestimate the amount of harm they do to others, and underestimate the amount of harm they do to themselves. It takes bravery to rectify a bad decision, but it is the kindest thing you can do for yourself. Even more importantly, taking responsibility for your mistakes helps to develop the priceless gift of humility.