My best friends girlfriend split up with him 4 years ago, they lived with each other for three years. She has been dating another man for the past 4 years, but my friend can't stop thinking about her and constantly talks about how good life was when they were together. They both still keep in touch through emails or texts and sometimes phone calls, but I feel this woman is just stringing my friend along. He compares every woman he meets to her; he says he wants to find a really beautiful woman so he can show her off to his ex girlfriend. He gets so depressed if she does something to make him think he's not going to get her back and his life is just standing still living in the past thinking about this woman and how things used to be. I am very concerned for his mental health and I would really like him to move on and be happy again. What can I do or say that will help him let go of his past relationship and move on? I feel it has become an obsession.

Take him for coffee and then ask him to wake up and smell the coffee... :)

Physically taking him out and hitting him with that symbolic phrase may strike some meaning in him. While he's open to the meaning of that phrase and the location he happens to be in at that moment, ask him to think about how she's spent the last four years and how he's spent the last four years. Lay it out openly and honestly, as you see it.

He has to be the one to acknowledge he is living a fantasy that will never come true, and get out from under the shadow of her memory.

What can I do or say that will help him let go of his past relationship and move on?

Was their relationship really that perfect? Maybe you should start reminding him of some of the bad times they had together.

Yes, I've tried this but he seems obsessed by the thought of this woman. I have tried to analyse the situation and I can only think that his ego has been hurt and he can't believe that he has been deceived. My friend seems to think that his ex is always thinking about him and the places they went and things they did, but I tell him he his living in a dream world and he is the only one thinking of them things, she has moved on. But he doesn't want to talk about it after that, he is in denial and only makes excuses for her. Would a counsellor help or do you think he needs a shrink at this stage?