She left without saying anything to me. No warning or reason or goodbye, she left just like that. What should I do?

Keep busy, grieve as you need to and give it time. There is no quick fix for break-up pain.

Something similar happened to me. It took me a while to process. Then eventually I understood that who she was, and my actual relationship with her (and to her, and hers to me) were separate things from the relationship I thought I had with the person I thought she would be. The brain wants to simplify all that and the heart wants to hope they’re all consistent and going to be there the want we want them, but the reality is a separate thing.

And, when the reality became that she didn’t want to be in a romantic relationship with me any more, having those things separate let me realize I didn’t want that either, and that the fully working/lasting relationship I thought I had, wasn’t really the way I thought it had been, and wasn’t there at all anymore in any way I’d want it. That made for a very rapid shift from heartbroken to healing.

Oh, and although I don’t know either of you, I expect the sudden no-communication exit has to do with feeling guilty and not knowing what to say or do except knowing the need to get away.

Understand Codependency

Stop looking for the right person. Become the right person.

@abheem: Sometimes stuff happens to us that’s inexplicable and painful when it occurs. Sometimes those things have a way of working themselves out to where you end up in a better place than when you started. Call it fate, call it the Laws of the Universe, whatever. I’ve had bad things happen that ended up being good for me in other ways that I couldn’t imagine. Every cloud has a silver lining.

Rejoice in the fact that she didn’t rob you blind!

Exercise
Try P90X
Will take your mind off of just about anything

I’m sorry you’re hurting. Your pain is real and it will take time to grieve and heal.

We can’t explain why she has behaved as she has. Only she can do that. The reality is you will probably never find out why she treated you this way. I think @Zaku is spot on in pointing out that who you thought she was and who she actually is, and how you each viewed your relationship were quite different. You can learn from that. Perhaps she didn’t speak to you because you weren’t open to hearing what she wanted? Perhaps she didn’t want what you do but she couldn’t bear to tell you? Perhaps she’s a selfish bitch and it was always only about her? There’s no way to know.

So, take time and heal. Exercise as @josie suggests. Get out and see the friends you’ve neglected. Go and do things you’ve been putting off. In time the pain will heal. Sometimes, we just have to accept this is the way things are and to not over think ‘why’ things happened. Just accept it’s over and start to rebuild your life.

Count your blessings.

@abheem I am sorry for your loss. Painful stuff. You absolutely need to take time to grieve and then pull yourself up and out of that painful place and begin to live again. You may have “jumped the shark”. It sounds like she was using you. (with your permission). The reality is she’s gone.
Finish grieving and move on!