Broke up with girlfriend one hour ago and feel miserable, what should I do?

Give it 6 months.
If you have not gotten over her within 6 months, get some counseling .. because that would indicate you aren't going to get over her without some tools that the counselor can give you.

Look .. things happen in life. We do NOT always get what we want.
And until we learn to just relax with things we don't want, we will never be happy.
WE make our own emotions, and an inability to open up fully to how we are feeling and then to RELAX into them .. that makes us even unhappier.
Resistance and tension with pain (whether physical or emotional) ALWAYS makes the pain greater.

You doubt this? Think of little kids getting a flu shot in the arm ... compared to an adult. The child screams and resists and finds the whole experience utterly traumatic. The adult accepts and just relaxes . and doesn't even blink an eye. The difference is in our reaction .. it is not in the needle itself.
So the solution is to be ABLE to allow your pain to be there, and to relax with it anyway.

In fact, that is why you two fought anyhow .. because neither of you were able to work with your own emotions. Until a person learns to do this, no relationship is going to last and/or be happy.

Since you two were NOT able to make it work as a couple .. let go and move on.
Should you be able to get the two of you back together again, you two will just end up breaking up again. Because neither of you are yet mature-enough with your own emotions, to make it work. And because the two of you try to solve your unpleasant emotions by pushing the other person to BE a different person. This is why you two fight, and WILL fight if you get back together.

What would I do?
Walk away and spend 2-3 years trying to make friends with how I handle my own emotions. Talk with a therapist as a way to get started on this program.
Masturbate a lot, in the meantime.

Jesus Christ, you again? What's your end game here, just keep asking the same question over and over until someone tells you what you want to hear? Just say it if that's your plan, and I'll be glad to help. Watch...

What you need to do is get good and drunk, and stay there for at least 3 days. I don't mean upper-lip-numb, no. I'm talking fall down, drooling, karaoke singing, Motley Crue style wasted. And stay there for at least 72 hours. Then when your sight returns and you've swallowed a few bottles of Tylenol, you can begin the road to recovery.

Getting hammered doesn't kill the pain, actually it doesn't even dull it much, but it's what we all do so obviously it's part of the male healing process. Girls get a gallon of ice cream and a box of tissues and a sappy romance movie and cry a few buckets out, we get slobbering drunk and wake up in a parking lot somewhere.

Do that step first, then start healing. A few weeks from now, you'll be able to taste food again. After a month or so, you'll be able to wake up without that ripped feeling deep in your chest. Maybe a month later, you'll actually be able to smile again.

I know how it is, it was your first love and you were so in love it hurt, then things went south and now it's over. It's tough, I've been there so I know. I've been beaten to a pulp by pro kick boxers, and that was nothing compared to the pain of a heartbreak. But you'll heal, because we all do.

And look at the bright side: At least you didn't marry her or get her pregnant before you realized that she's a self-worshipping princess from hell. Because trust me, that would have been much worse.

Is a bottle of jack calling your name or is it ben and jerry's ice cream?