If you would like to apologize to your friend for your behavior, here is a simple template you can use to write a letter to a friend apologizing for your rude behavior. You can also send this over text or email.
Dear [name],
There were so many things that happened since we last saw each other. In fact, we had a big quarrel. During our last argument, I let my emotions get the best of me. As a result, I said some things I shouldn’t have said. I can’t blame you if you avoided me after that. Looking back at what happened, I regret saying all those things.
I admit I was wrong when I said all those terrible things to you. That was clearly not me. I was obviously not thinking correctly when I was angry that time. If only I could go to a time machine and undo things that happened, I would definitely erase what transpired between us.
I apologize for what happened and I will do anything to make up for it. I can’t imagine spending the rest of my life with someone else other than you. Hoping you would answer this letter as soon as you get it. I really miss you.
Truly yours,
[name]