Ironically, one of the best solutions is to look the girl up,
and try to be friends again. Do not do it with the intention of
getting her back, do it with the intention of sewing the rift
between the both of you.
There'll be great chance you'll still want to be with her if you've
made it to be on talking terms again... But if you have to let go,
you just have to. Some things just weren't meant to happen - like
why the moon never collides into Earth and just floats endlessly
round it...
Someday, you'll know why she wasn't meant for you... but for now,
just hold on to hope on yourself. =)
Choosing to blurt your feelings out here would indicate that you
are strong enough to let your problems be known and that you seek
help... Now all you need is to be strong enough to pull yourself
through!