move on! Being in the past will prevent you from moving on. When a thought pops, change it.. OR revel in it and remember the moment for what it was.. living in the past will also prevent you from seeing what is in front of you. it's never a good practice.. having memories and such is ok, but dwelling? never. I did it back in 99.. took 7 years to move on with heavy counseling the last 2. i made bad decisions in that 5 year span, got involved with the wrong guys and married an abusive alocoholic, i'm now divorced lol. that's what dwelling got me into.. so nip it in the bud and go seek professional help now. they will give you the keys to stop the nonsense, you just need to be honest with the Dr. about your thoughts and feelings and they will help you get over it.
good luck to you.

Think about why you still think about it. Was it not your choice to end it? Was it a bad situation? Is there something specific that keeps popping back into your mind? If after you answer these questions, you still are thinking about it, maybe you need to re-evaluate why you're not with this person. Maybe it is a sign that you might have made the wrong decision. If not, try to do something to keep your mind occupied. It seems silly, but get a hobby!! You would be surprised what doing something you like to do can do to help all kinds of things... depression, sadness, anger... all the negative feelings that you have can be changed. I think my shrink called it Transference... taking one set of thoughts and replacing it with another. I don't even think about what's his name anymore...lol! They are just memories by the way, and we wouldn't be who we are without them. Who's to say you can't remember the relationship, if it was a bad one, at least it will be fresh in your memory so you don't make the same mistakes twice! ~Kacey~

sometimes it takes a while to move on. It has been 2 years since my friendship ended, and I sometimes find myself drifting back to that time. Sometimes it helps me to know that no matter what happens, we could never go back to the friendship we once had. I still miss this person, but you just have to move on with your life

Without knowing the specifics of this relationship you speak of, it's hard to say. I am in a similar situation. I think 'time' is the only thing that will help you move on. Also, think of why you ended this relationship in the first place. Remind yourself that this is better for you and your peace of mind. You may still think of this person, as I do, but it may help you eventually move on.