I can empathize what you are going through, and I have made MANY posts in this forum in regards to people who have experienced break-ups.
I recently went through a breakup, and yes, it's somewhat depressing since thoughts of your ex-girlfriend always seem to wander your mind. My advice is to keep yourself busy doing things, continue to hang out with your friends every chance you get, and avoid sulking alone as much as possible. A DJ in this forum pointed out that getting over an ex-girlfriend is quite like trying to quit smoking: You gotta stay away from the cigarettes themselves and anything/anyone that will remind you and make you want to smoke again.
However, I do have 2 posts that I have taken from DJ's on this site and possibly other sites which I copied into a word document to re-read over and over again to help me get over my ex, it might help you as well.
The first one: (I take no credit for it, just to help a member on this site.)
Find comfort in this: We all thought we had "the one". It's so pervasive that seduction books even have this documented! Think about that...How is it possible that so many guys seem to have lost "the one". I mean, shouldn't it be hard to find her? If she's so hard to find, then why have we all found her, maybe even more than once!
Add to that that you often realize that she's "the one" after she breaks up with you. It's just your pain playing tricks on you. You'll think back and only remember the good times, how glorious and lovely they were. You'll forget the bad times, the boredom and her bull****.
Be sure that there is no "one". There will be women who approximate what you want better than others. But probably the biggest problem is that you don't actually know what you want. For me a kickass woman would combine traits of 2 of my ex's, and yet each one independently is lacking. And yes they were "the one" too.
And yet despite the relationships i've had, I'm still not sure I know what I want. For example, I've never been with a girl who can genuinely make me laugh. Maybe if I had been, that would be an important trait for me to look for. Maybe that's just the trait I'll need in my partner when I'm 90 yrs old and pissin in a bed pan.
In any case, this is like speaking logically to a woman. You can't just come out of this through "logic". It can only take you so far. You need other things in your life to start buffering your current emotions. You need other emotions in your life that start eating away at these and leave you no time to feel or think about her.
Second post: (This one made me laugh the first time I read it, and it was probably the first time I did laugh after my girlfriend broke up with me.)
I broke up with my hs sweetheart of several years when I was 19 and thought it was the end of the world. Now she's fat, and I'm glad we're not married. Later in life, my wife of seven years divorced me, and I thought that was the end of the world. Now she's fat, and I'm glad we're not married. Recently, my gf of a year dumped me. It sucks, but in a couple years, she will be fatter, and I will be glad we're not married.
Anyway, hope I helped you out. Most DJ's in here will just tell you to go date other women. Once she finds out, her jealous genes will trigger and she'll ask for you back. And the moment this happens and you realize she wants you, you'll notice you won't want her as much anymore.
Think about all the starving people in 3rd world countries and how horrible their lives are at this very moment. Soldiers are getting blown up on a daily basis because of war and many men find their spouses cheating on them. The world isn't perfect, and I completely understand you were with this girl for a long time and you may have had a vision that this girl was completely perfect, but it wasn't. It never was. Forget her.
You're 20 something, correct? You still have your youth life to live! You seem to have quite a bit of game, and you must be attractive if you were able to pick up a girl like that. You got everything all going for you so be thankful. Everything in life happens for a reason, so who knows, maybe another chick will enter your life. Or who knows, maybe even more!
Also, this is something I learned the HARD way. Many DJ's on this forum say to get over a girl, start seeing many other women because it does two things for you.
1) When you surround yourself with plenty of women, your mind gets carried away from that girl you claimed you love so much, and it makes you realize there are plenty of fish in the sea.
2) If the women you broke up with sees you with plenty of women, she will fill with remorse and regret breaking up with you. Most likely, she will apologize to you and feelings will start to emerge within herself. Jealous is KEY in women. Hopefully at this stage, by realizing that she wants you, you will not want her anymore. (Once you realize you are able to get something, you don't want it anymore.)
BUT when you approach these women, don't have the mind frame that you are only talking to them to get over your girlfriend. THIS IS THE WRONG WAY TO GO! If you go this way, you will only see yourself thinking about that girl more often.. it happened to me.
Try out this routine: Channel your energy in a sport/working out and other physical activities for about 2-3 weeks. If sports aren't your thing, focus on getting your grades up. Chances are that when you had a girlfriend, quite a bit of your time involved her in some way whether it was meeting to go to the movies or talking to her on the phone. Fill up that free time with activities so it's not filled with time to mope around about her! I, personally, wanted to get my grades up because I found they were really lacking when I was with my ex-girlfriend. Than start meeting girls, etc.
In short, when you break up with your girlfriend and you want to start seeing other women, do not have the mind frame that you are only meeting those women to get over your ex-girlfriend because it will hit you right back in the ass and your mind will only consist of even more thoughts of her.
Best of luck with everything. If you have any more questions, feel free to PM me and I will be glad to help you out,
Axcell.