When it come to the one that gone away, I have quiet a few and the turth is that, I never regreated it. Because I believe I did the right thing. When it come to relationship I got a few motto:
1. Remeber this girl no matter how much you like her or want her, having her is not a necessity, it is a luxary. So, don't go around pulling those romeo and julia crap, it is stupid.
2. Remeber what you once have, but learn when you need to let it go
3. Always remeber, will you feel sadden by them leaving, if the two of you never met, sometime that is what you need to do, pretend you never met.
I had let go of a lot of girls that can be consider as true love and I never regreated any of them, because in my opinion, I did the right thing, by letting them go. It suck, but if I am to do it again, I'll do the exact same thing, all over again.