Unfortunately there is nothing you can do. You will always think about someone you have loved and lost. In time though you will notice you think about them a lot less frequently and it doesn't hurt nearly as bad and someday those memories just might make you smile without the hurt.
First you need to get rid of things that remind you of her. If she gave you any gifts, either donate them to Goodwill or another charity, or bury them in your backyard. Then get busy doing all the things you didn't have time for when you were with her. Get a new hobby or improve on an old one.
There's nothing u can do really..u can try to spend time with friends and just get ur mind off of it by keeping busy...but when it comes down to it..the thought isn't gonna go away all of a sudden..u just need to give it time and you'll feel better..whether a few weeks like some people or a few years like mee..you'll eventually get over it...just give it time..distracting urself is only temporary..so just give it time and don't try avoiding it too much:).,