Why am I so jealous?

One of my really close friends is now going out with the guy I like, and they're perfect for each other. The guy has liked her for a long time, and I can't blame him- she's the perfect girl. I was really close friends with the guy two years ago, before he knew her. We kind of drifted apart, and it was partly my fault because I didn't talk to him much but he didn't talk to me either. And I think he completely forgot that I exist. Because he forgot that I was in two of his classes, even after eight months. Yeah... But as hard as I'm trying to be happy for them, I can't and I feel so shitty. How can I just not be jealous? It doesn't help that I've never gone out with anyone before. I'm not ugly and I have been asked out, but I just didn't like the guys that asked me out. Not like the "I'm to good for you" thing, I just had no feelings whatsoever for them. Advice? I feel like I'll never ever meet "the one." So tired of waiting.