Yah I've been there too (about girls though, as I'm a guy lol).
What I tell myself now at 25 though is that... if something didn't work out... then it just wasn't "meant to be" :) Not in like a fate way, but more that if two people are really, really right for each other, then everything will work out in the end! :) And if not? Well then there'll be someone out there that you WILL get along with better, and then it will work!
That always makes me feel much better now if something goes wrong to do with rships! heh - hope it helps! :)