We have all done things that we regret. The bad feeling we have when we break our rules is guilt.
In life we make mistakes, hurt people (often unintentionally), and sometimes fall short. Guilt feels bad to help us try to do better and avoid future mistakes, hurting people as often, and trying harder to live up to who we want to be.
People react in many ways to guilt. Think about which kind of reactions help you move forward in your life and resolve issues as best you can. You can't go back in time and undo what has been done, but there may be some things that can be corrected or changed.
For some people guilt can shift from "I do bad things" to shame "I am a bad person" where people feel helpless to change anything, because they believe their very nature is that they are bad. This is an incredibly painful experience for the individual. It also hurts the people around this person, as the person will usually isolate, or even lash out "I'm a bad person anyways, I might as well".
Breaking the cycle of heavy guilt is difficult, and people often don't reach out for help because they aren't sure they deserve to get better. I encourage you to reach out to help you deal with the heavy weight of guilt. You being in a better headspace will benefit yourself, and everyone around you.