It sounds to me like you already told him how you were feeling and what you want, which is for the two of you to be a couple, and he for whatever reason, doesn't want to do that (it doesn't even matter why, don't waste time on it, you could be speculating about that to the end of the world). I can understand wanting him in your life because you love him and not wanting to deal with the heartache of breakup. But I think that by doing so, you'll just prolong the pain and also be emotionally unavailable to the prospects of other relationships.
I don't think you can learn how to not care for someone while being in constant contact with him. I think that many women bring themselves into situations like that hoping that the guy will change their mind or that they could somehow win the guy over. In most cases, that doesn't happened. Just think of how you'd feel once he falls in love with someone else and I think you'll realize that being friends might not be the best idea.
One of my best friend is a guy I used to date pretty seriously, nowadays we are friend but it took 4 years of not talking to one another as well as working on the friendship for a long time afterwards. My advice - tell him that you can't see him anymore because you want things he can't give you, and move on.