When it's a lost cause but you can't give up

Two years ago I met the perfect man for me. The problem was, I had literally just finished my A-levels, and he was 23 and had a degree and a good job. We got on really well and were attracted to each other, and on several occasions things happened between us, but in the end he didn't want to pursue a relationship, mainly because he thought I was too young. We worked together for a year, and then a year ago I went to university. I thought about him all year, and just haven't been attracted to anyone else, even though I've met loads of guys, and been asked out a fair bit. A couple of times during the year I tried to kind of lower my standards, in that I started seeing guys I wasn't really all that interested in, in the hope that I would get more enthusiastic about it after a while, but it didn't work. I also realised that I go for older guys, and I'm not likely to go for anyone at uni for this reason. (I always thought my ex was a bit on thr young side, and he was more than a year older than me and has now graduated and got a job as well.) Anyway, this summer I've been back in my old job, and I still can't shake this guy from my mind. We are good friends, but I can't get over the fact that he is my perfect man, and I don't want to be with anyone else. I think that when I was 18 I was too young, but now I have more life experience and the age gap is less significant, but it seems like any chance I ever had with him has gone. Still, I don't want anybody else, and I know that it won't go away until I meet somebody else, which probably won't happen for ages. (I'm just hardly ever attracted to people, I don't know why.) What would you do if you were me? I feel I should move on, but there's nowhere to move on to.

I think Libertine is right, 23 to 18 is not a massive age gap, saying someone is a bit young is a convenient excuse to let them down gently