a Forgiveness Letter?

It's easy to think that in a letter you can "said" more things than in person to person. Only take a pen and a piece of paper (or in my case a computer) and the words seem to sprout for itself. You can do an introspection even try to psychoanalyzing by yourself: I did "that" for ...(a list of motives). Maybe you can't find the reasons (someone said me that) but at least you try to open yourself
Example:
Dear XY: I don't know how to beginning these words, is so common but I really feel it: so sorry. Sometimes I don't see what really matters and give for done the things that I have in my life. I can't justify what I did, but everything has turned a nightmare. That first error created an domino effect domino and now I can't repair all the damage that I done to you. I remember the happy moments with to you by my side, the expression in your face when you're saying to me that you loved me and now, all that we were sharing has disappeared. I know that I can't ask you for forgiveness, but if you're giving me a chance I swear to you that I would do everything possible for be who you want and wait and I'll compensate each of your sufferings with happy moments. I really love you, XX