(Desire) So you really want to be with that person, and you know that there is nothing that can happen that would make this change. He can go out with someone, someone can come into your life and no matter what you still want to be with them. This is important because if there is a part of you that doesnt really want them, it wont work.
(Allowing)Next you have to work to change things that went wrong with your relationship, be honest and look at things. Work on them , work on yourself. Go out with friends, be happy... feel and look more attractive.
(Detach) Come to the point where you know you belong together but you just let go. You let go of the feelings, good and bad and just go out and focus on yourself. Dont say well hes not coming back, but say im not going to worry or think about him , i will be happy either way. This is the hardest part. Think of it this way, the more you think about how you want him back the more your sending the vibe hes not with me. When you change that vibe, you get what you want.