Whether you were dumped or did the dumping, moving on can be equally difficult. Break ups suck and its hard to let go. You've spent the last however long you were together thinking that your partner was the one for you, only to find out that you were wrong. It can take time to readjust your world view and get to know what its like to be without them. This can last six months, a year, or two weeks - depending on how well you are at adjusting to changing times. Don't let others judge you for moving on too soon, you can't keep living in the past. The relationship is over, move on.
Deal with it.
Be upset, be angry, be hurt. Let it all hang out and deal with your feelings. It sucks, no breakup is fun. the recovery time can be difficult. You might need to cry, to drink yourself into a blackout, to go on a slut rampage through the city. Once you've finished processing the hurt you can head on over to the next stage: acceptance. Be as emotional or unemotional as you need to be. You've lost someone, it's OK to be sad about it.
Recognize it is over.
It is over, it's done. The past is in the past, and that's where it should stay. You broke up for a reason, and that reason may still be there a few months down the line. You can't keep holding out hope that they will change and you will get back together; that everything will be perfect and you'll have to perfect boyfriend/girlfriend. Love isn't about acquisition, love it about appreciation. You shouldn't have to mould your partner into the perfect boyfriend/girlfriend for you. You should love them for who they are, and you should be loved for who you are. It's over. Leave it be. Don't put your life on hold, let the relationship go.
Living in the past more than the present.
You know what's fun? Life. So why not go out and experience it. I know it can be difficult after your heart has been cleaved in two but what better way to recover than to prove to yourself that you still have a life and friends, and interests in romantic pursuits. Just because one relationship failed it doesn't all of yours have to. You have so many experiences ahead of you, so many more memories to create. Quit living in the past. The times have changed. No one is going to want to sleep with you if you're hung up on your girlfriend who dumped you a year ago.
You've changed, time to recognize who you are.
If you had a relationship that stayed with you through to college it can be hard to keep yourself separate from your girlfriend/boyfriend. You've grown up together and your friends see you as one single entity. College is a time of transition and new experiences. A lot of relationships don't survive that transition and after the relationship falls apart both parties can feel like they're lost. Not really knowing who they are and what they like. Were they only watching that TV show because their girlfriend liked it? Were they only wearing those clothes because their boyfriend said they looked good in them? No, you're free of someone else's opinion, you only have to think of yourself when it comes to how you behave, dress, live. You can do what you like and get to know who you are. Not in spite of your previous partner, just for you.
Avoid confrontation and conversation.
There may be a time in the future when the two of you can be friends again, but that time is not now. You need to distance yourself from that person and recover and readjust your world view. Learn what the world is like through your single eyes and not as one half of a loved up couple. You may start recognizes things that you never had before. Like that your boyfriend grew into a douche without you even realizing it. By continuing to surround yourself with a person whose heart you've broken, or who broke your heart, you're encouraging festering feelings, anger and hurt. It's not a good mix. If you're one of those couples that constantly breaks up and gets back together again, stop getting back together. Find someone new, who isn't exhausting and doesn't spark drama in your life. Like I said, you may be friends with that person again, or maybe you won't. You might realize in a few years that that person who once meant the world to you is now a stranger, and that's OK.
Don't let it hold you back.
Have you always wanted to travel but didn't because they didn't want to? Have you always wanted to try a new kind of food but their criticism or distaste got in the way? Did you stop wearing your favourite clothes, eating your favourite foods, doing your favourite things, listening to your favourite music, all because of them? Who cares. You are no longer a part of each other's lives. You no longer have to put up with their inhibitions and can do whatever you want. You can be whoever you want.
Don't feel guilty forever.
This is mostly for those who did the breaking up. You weren't happy and instead of looking out for someone else's happiness - someone who clearly wasn't concerned with yours - you looked out for yourself. There is nothing wrong with that. You shouldn't be saddled with the burden of someone else's mental health and happiness unless they are your child. You don't owe that person your life. If you meet someone who does make you happy and doesn't expect anything from you and is appreciative of who you are, why should you feel guilty about going for that person? They are clearly great. Some people say that you should wait until a few months have passed or until the other person moves on, but I disagree. We only live once. Don't punish yourself for trying to make yourself happy. You're allowed to go out and live your life, so do it.