You're probably thinking about him or her all the time.
Everything reminds you of that person. The coffee cup they used to drink out of. The blanket they slept under. The places you used to go. It's natural and normal. As social creatures, we're biologically programmed to take rejection hard. In the old caveman days, rejection could literally mean death. You're not pathetic. You're normal and fine. You'll get over this. Time heals all wounds. Yeah, yeah. Let's speed things up a little.
Distraction is essential. Now is the time to keep as busy as humanly possible. If you are a parent, indulge your kids in the best quality time they've ever had, because your kids will bathe you in delicious love. That will feel terrific.
If you are on your own, and have the time, consider getting involved in a group with kids.
Volunteer to read at the local library. Help out at the local Boys and Girls Club. There is nothing like kids loving you to make you feel terrific about yourself.
Not interested in kids? Still feel like you're not interested in anything but the couch? Drag yourself off it anyway and start doing something that involves your BRAIN.
As stated before, distraction is the key to make that stupid healing time fly by so it can work its magic. Ever wanted to learn a language? There are many online courses to help you do so, and they're all free. Practice on your plants, on your dogs and cats. Enroll in a class at your local community college -- this has the added benefit of involving you with other people, and possibly introducing you to new, fun friends.
Take voice lessons.
Or learn an instrument. Or learn how to design web pages. Or involve yourself in some professional development; this could be a key thing to do, because often the circumstantial depression involved with heartache can affect our jobs.
Write, write, write.
Get yourself out to the nearest stationery boutique or home goods type store, or Barnes and Noble, and splurge on a good, solid, maybe even leather-clad journal. Write it all out of you. Swear, cuss, write your old loved one letters -- but do it here, don't send any.
Stop talking to your friends about him or her.
You've probably done it a lot already. They're tired of hearing about it, and it's not going to do you a lot of good to keep running it over and over. You can't forget. But you need to take a break. Try to keep conversations positive and fun for a while.
Go to the movies.
Try even going alone. It's not that bad. You get all the popcorn to yourself. And you never have to argue about what you're going to see.
Keep telling yourself you are a good person.
Because you are. It really IS the other person's loss. Some people just don't belong together, and some people are just idiots. Either way, it's over. Accept it. That's the toughest part. Don't call, don't write, don't try to make contact. You will be SO glad you didn't later on, when you still have your self-respect.
Remember always, when you're busying yourself, concentrating on you, getting stronger, making yourself a better person -- that it's when you least expect it that the right person comes along.