I've given this advice before here in one incarnation or another, and I will give it again in the form of a list:
1) Delete her number, delete her from Facebook, take down everything in your living space that reminds you of her (within reason..don't throw the puppy in the trash or anything). Unfollow her from twitter, Instagram, anything that will allow you to Internet stalk her. Also anything that will allow you to real-life stalk her. Get as close to a wholesale cleaning as you can. After 6+ years, that's going to be impossible, but get as close as you can, even if it means some tough choices. If she asks about it, tell her that you don't think you can get over her any other way.
2) Take a few days and lick your wounds.
3) But not too many days. Stay active. When in public, pretend you're okay. It's easy to slip into melancholy and full on emo-indulgence. RESIST.
4) Be social, but don't be weird about pretending like its fine to go places you know she'll be, especially if alcohol is involved. But be as active as humanly possible . Play lots of pickup, go out for pizza. Anything to stop yourself from wallowing after those first couple of days.
5) Don't allow yourself to be petty. Don't engage in grapevine communication, and if you can, don't talk about her at all except to your most trusted of friends. You've spent the past 6 years devoting a lot of your life to her, and it's a fine line between love and hate, it's easy to re-purpose those good feelings and attentions you used to get by interacting with her into bad feelings and arguments, RESIST.
6) Keep on pretending you're okay, keep on being a good guy, engage in a rebound or two, pretend that you're just living your life like it doesn't phase you. Eventually, you will be okay, you'll be unsullied by crappy breakup drama, and those rebounds will transition into healthy emotional relationships.
7) Get yourself into the best shape of your life. Feeling good about your appearance and by default, feeling good about yourself will make every single thing I outlined above easier.
It's gonna be tough, but you'll get through it.