So, whatever you do, don't kill her and chop her into small pieces for ease of disposal.
Damn, there's my number one suggestion gone.
In all seriousness, I can't really add much that hasn't already been said. You seem to at least have a mature attitude to it (not that it'll mean it hurts less, but it's a start).
Every relationship is unique so there's no one-size-fits-all solution unfortunately. Plus I'm pretty rotten at being dumped - I've never stalked anybody, but I've spent far too much time beating myself up about things that ultimately I had no control over.
Whatever you do though, don't let it have a lasting effect on your self esteem, and any decent person should at least be adult enough to give you some indication of what went wrong. Otherwise it's downright cruel and you're probably better off without them in your life.
I really don't want to spout the hackneyed 'time is a healer' stuff, but unfortunately that's the truth. Meanwhile, as suggested above, just try to spend as much time around good friends as you can.
That sounded really lame didn't it? Hope the pain eases before long somehow.