Yeah at first it does feel like a bereavement, you'll probably have trouble sleeping, not much of an appetite and like you say want to be alone.

Then yeah as you say 'Hate' comes in, but it's not really hate. It's just confusion, you're frustrated, angry at her, angry at yourself perhaps trying to rationalise what you did or didn't do to make her feel she wanted to end the relationship. You may also feel bitter. Unfortunately this is the stage that can last the longest and hurt you the most if you allow these emotions to consume you. It's normal to feel this, but it's abnormal to dwell on it for too long.

Try and be as amicable about it as you can be. Be cool and polite with her but don't try to get her to 'see sense' or change her mind, avoid being friends with her if that's what she asks for. At the moment I don't think you can handle the thought of her seeing other guys, so to be her friend right now would not be something I'd recommend. In the future when all's well, then perhaps you might genuinely want to be her friend.

Don't hate her for what she has done to you as she hasn't actually done anything to you that deserves a hateful response, relationships start and end all the time, it's a natural cycle. You're not as naieve to think 'Love conquers all' and 'Last forever' because in reality, it doesn't.

It's cliche but true - 'Time heals all' in a few weeks/months you'll feel better and probably cringe at how much you allowed this to affect you.

You're probably about 21/22 now. I went through the exact same thing at that age after a 3 year relationship, you need this to happen to you and feel at your lowest ebb in order to never allow yourself to experience those emotions again by bettering yourself, you owe it yourself not to feel like this anymore. It's called growing up Jynx, everyone goes through this, it's how you respond from this that will help define who you are.

Worst thing you can do right now is get drunk all the time, that wont help you forget that will just exacerbate your anxiety and make you send chodey texts or call her needlessly. Don't listen to any Smiths or read Schopenhauer in your current state! - It might send you over the edge lol!

You're ego is perhaps bruised as well, don't try to nurse it, just let it die.