Dream of

I once had a very good friend. I kind of liked him but we were not in a relationship. Then due to some misunderstandings we went our ways (about 3 years back). The parting was not really on a good note. He said a few things that hurt me and just shut me out.We did speak once after that about 2 years ago.Now that I am happily, why do I still dream about him. In my dreams even though I see him, we do not talk. I just look at him and then suddenly he goes missing and I feel sad.I usually wake up after that.What does this mean?