"If you love someone, let them go. If they return to you, it was meant to be. If they don't, their love was never yours to begin with..."
This is a really tricky one..
I had this sorta problem. Was having a casual relationship with someone, I thought it was more than it was. He went off with some other girl a few times, and each time, i'd think about hooking up with someone (who i also liked and he really liked me) and decide against it in case he changed his mind. Yeah he did at times, and I got what I wanted, but I also didnt. By not moving on, he knew he could have me, and I was being used, and I fully well know it.
But then, had I gotten with other people, or looked for someone else, in a way it would not have been fair, because I still did (and do for that fact) really like this guy, and all the others I met never compared.
I say just go with the flow. Don't look for a relationship of any sort, but don't do what I did and avoid one. If someone reallt great comes along, yeah they'll definatley help you get over this person! But if someone not so great comes along, don't just go with it and hope for the best, because it probably won't.
At the end of the day, if you make it obvious you'd have him back/go back to him straight away then you'r losing out. Get on with things and let him make up his own mind.
Its tough though.
Also, what a previous poster had said I agree with too.
Sometimes a one night stand can sort your head out. Strange but true. Although obviously they arent for everyone (thats fine) and you shouldnt just go looking for one for the sake of it, but if one comes along and you want one, I wouldnt say its always a bad idea.
Sometimes however, they just make you miss/want the other person even more.