#1 Do The Right Thing
If you have done something wrong and you know that it's wrong, usually, you'd feel guilty. Honestly, the only thing that you can do to make the guilt go away is to do the right thing- for example you have accidentally made your friend cry or you have saddened her, say sorry. That "sorry" would not hurt at all and trust me, a simple sincere sorry is better than having to go through something worse like losing that friend.
#2 Do Not Think Of It All The Time
If you think of it almost all the time, your time would be wasted. I say get up and do some action, solve this problem. Dwelling on the thoughts of guilt will not do anything, it will just make you feel worse. As I said in #1, Do The Right Thing.
#3 Open Up To Someone Whom You Trust
At some point, you will have to open up. If you just keep this to yourself, you will feel bad. But then if you open up to someone like your mom, your dad, your siblings or to anyone you trust, they might be able to help you and talk to you to make you feel better. They might even give you more advise! :)
Photo from Tumblr
I hope that this has helped you guys, have a great night! :)