Been there, done that.
Helpful advice?
Don't drink.
Don't ask CAG for help. Especially in the OTT.
Doing either of these things will lead to some serious depression / suicidal tendencies.
What you have to do is move on. Don't beg for her to come back, don't try and "fix" it. It's over and you'll have to accept that. Doesn't mean you guys can't get back together, just means you can't right now.
Stay busy / active. Go exercise, play some games, hang with some buds, concentrate on work / school, even talk to other girls. There's tons of chicks out there, more than likely better than what you had. You just have to look for them.