The most important person to be able to forgive is yourself. You can avoid others if you harbor resentment and hurt feelings, but you're stuck with you. Wherever you go, there you are! So it is important to let go of your mistakes, let go of regret, and forgive yourself.
You cannot change your past actions any more than you can change the actions of another. You have to find a way to come to peace with them and move on. Everyone makes mistakes. They're in the past though, so take whatever lessons you can learn from them, and leave them in the past where they belong.
Sometimes doing something to "make things right" can help you to feel better about yourself and move on with your life. A charitable action, a gift, a good deed, or even a simple apology could help. But don't take it too far. You could spend your whole life trying to "make things right" if you let yourself get wrapped up. Allow yourself one shot, whatever it is, and then dust off your hands and call it a day.
An Effective Apology
I've been going through a particularly rough time lately with my pending divorce. During the first few days, I was a wreck. I lashed out towards some people who did not deserve it. When I had some time to think more clearly, I felt awful for my hurtful actions. I decided an apology was in order, so I wrote an apology letter. A very effective one, both for making the other people realize that I am sincere and for making me feel at peace with the situation once again.
The keys to an effective apology:
NO EXPECTATIONS! You won't get the peace of mind you want and you will not come through as sincere if you create your apology expecting some sort of action or response from the other party. Just apologize and leave the rest up to them.
HAND-WRITTEN- If you're trying to apologize to someone, there's a good chance they aren't happy to hear from you. A phone call can be ignored, an e-mail or text easily deleted, and in-person interactions can spiral out of control. A hand-written letter is unique in this day and age. If someone sends you a handwritten letter, you will read it.
ACKNOWLEDGE THEIR FEELINGS- Do not simply address the actions. This will come off as the forced playground apology. "I'm sorry I pushed you down...(reluctantly with mom scowling over). Take a little time to address how your actions may have affected this person. How do they feel? Address their feelings in the apology letter.
ADDRESS YOUR FEELINGS- Let them know that these actions have affected you as well. They must have, if you were so motivated to write an apology letter, but you must let them know how.
OFFER NO DEFENSE- You being defensive will only bring their defenses back up. Are you looking for their forgiveness or are you still trying to make them see things from your point of view?
After sending this letter, following these guidelines, I did not receive a response. I did not expect one, and I made that clear in the letter. I saw these people for the first time since all of this today, however, and received a heartfelt hug and a solid handshake. They expressed how much they appreciated the note I had sent. A little apology goes a long way to make everyone feel better, as long as it's truly meant. I'm sure I will never see them again, and that's fine. I think we all have come to peace here.