If you have broken someone's heart, and you want to repair your relationship with them, say "I'm sorry for breaking your heart" to them. Lots of times. Every chance you get until they tell you, "I know". They will probably act like they don't want to hear anything from you. The wall they have up, where you are concerned, is to protect themselves from you. You've been dangerous in their life and they still see you that way, even if they look like they have healed, you will never be welcome in their life. They need your apologies to be healed of the pain you left them with.
Do not defend yourself with excuses for what you did, just say you are sorry. You have to really mean it. Practice saying it to yourself if you are not really sorry yet and wait until you mean it. Keep your excuses to yourself or the apology will mean nothing and it will be worse than it already is. Both of you know that you were selfish and did not care whether you were tearing someone apart. A broken heart hurts, a lot. Probably more than you can imagine.
It takes courage to face the challenge of easing another person's pain before you can be concerned with whether you may be forgiven. You may not be forgiven. That can not be the reason you apologize. The reason is to give the person you hurt the gift of the possibility of healing from a stunning amount of pain.
If you are fine with what you did, the pain you have caused this person, I guess this letter is not for you, but consider that you might be cold-blooded and in need of growth as a human being.
I believe we all can grow.
It takes time.
