Why am I dreaming about my ex-best friend? :(

For about 2 weeks now, every night I've been dreaming about my ex-best friend. Some bad things happened and split us up, and I just wanted to talk to him about it all. But then I didn't, and that's when the dreams started. I was apologising to him, he was apologising to me, we were talking about what happened, and we became friends again. Too bad it's not like that in real life.
Why am I dreaming about him? And what can I do about it? :(

Callum