This is one of the best questions that I have seen in a LONG time.
I was in that situation. I basically spent the 1990s heartbroken over a girl that I wanted to marry but that dumped me in January 1992 just after I turned 29... I was always emotionally monogamous with her. I had to make a decision to let go - not an easy thing to decide or to implement. Indeed, we did have communication as recently as 1997.
I was resigned to being single the rest of my life but it was not some decision that I made. However, like the time just before I met that girl, I decided to "let life happen to me" which worked out well since that's how I met her. In other words, when I tried getting into relationships, that was problematic, but when I let life happen, I had better relationships...
Anyway, when I was 32, I did have a brief rebound LDR with a Canadian woman. It was a disaster. That's when I really made that decisions to let life happen. By 1999, I was interested in 2 women: 1 was 15.5 years older than me and very hot. The other was almost 16 years younger than me and very innocent. The nice thing about them is that they made me feel undead. I couldn't have a relationship with either of them, but I did meet my wife in 1999 also via email through work, but I met her in person in November and we became a couple shortly thereafter. I was 36. She was 42. We were married not quite 2 years later when I was 38.5 and she just turned 44.
So, my advice is don't become desperate and don't give up, but simply take it easy. Use a dating site maybe - they didn't have that when I was younger. If you are in a setting around men, there will come a point where you will meet a man who will put a spark in your heart.