Say something like: “I wanted to write you a letter to apologize for what i did”.

Say something like: “What I did last weekend was horribly inappropriate, disrespectful, and wildly selfish. Your wedding is supposed to be all about your happiness and celebrating your love. By proposing to Jessica, I turned that focus on to me. I tried to steal your moment and that was wrong. ”[3] X Research source

Say something like: “Jacob told me that my actions ruined not only your experience of your wedding, but also are now making your honeymoon less than the incredible experience that it should be. I hope you understand that that was never my intention. I wanted you to be able to look back on this time and remember only happy things but I have ruined that with my selfish actions. I’ve robbed you of those happy memories. While I can’t truly know how this feels to you, I can certainly understand that what I did was one of the worst things I could possibly have done to you. ”

Say something like: “This is an especially terrible thing for me to have done to you after how warmly you have accepted me into your family. You have not only shown your incredible, beautiful love to my brother, but you have also shown me support and kindness that I never could have possibly expected. To hurt you in this way was an insult to all the things that you have done for me and I hate myself for that. ”

Say something like: “I would try to offer an explanation for what I did, but there are no excuses. My intentions, though good, don’t matter here: only my poor choices. I absolutely take responsibility for my selfish actions and the terrible pain I have caused you. ” Don’t make excuses for your actions but you can explain your reasoning very carefully. If you really feel like it’s needed or would make the situation better, you can explain why you made the choice that you made. This should be done only if you think understanding your choices would give the person you hurt some comfort.

Say something like: “But just being sorry isn’t enough. You deserve better. When you come home, Jessica and I would love to throw a big welcome-home party in your honor. This will be the party to end all parties and it will be 100% devoted to celebrating the incredible love you share with my brother. If you would rather not do this, that’s fine: I just want to find some way to help you create the incredible, happy memories that I took away from you. ”

Say something like: “I can’t expect your forgiveness, though I certainly hope for it. All I can say is that I truly want things to be okay between us. I want you to feel okay and eventually even happy when you’re around me. I want to earn back the wonderful relationship that we had. Hopefully, in the future, we can find a way to move past this and create happier times together. ”

“Mistakes were made. . . " “If” statements like “I’m sorry if your feelings got hurt” or “If you felt bad about this. . . " “I’m sorry that you felt that way. "

You’ll also need to adjust the syntax of your letter to sound formal and better fit the situation.