Cut off all contact with your ex. Don't call him, text him or email him. Don't check his social media page or ask mutual friends about him. Ending communication will help you stop thinking of things to say to him.
Spend some time wallowing. Have your girlfriends over, eat ice cream, watch sappy movies. Feeling a little sorry for yourself is part of the healing process, so long as you don't stay in that mindset forever.
Focus on what went wrong in your relationship. Remember the times he hurt you or took you for granted. Feeling sad about a guy may make you remember him better than he was, so remembering the negative can help you keep perspective.
Focus on the positive aspects of the breakup, such as how you kept a straight face through the ordeal, how you've been spending more time with your best friend or sister -- a relationship that might have been neglected while you were still dating. Focusing on these positive things surrounding the breakup can help you to cope with the breakup and feel more confidence, happiness and other positive emotions, according to the American Psychological Association.
Get your mind off the breakup, however you can. Get a new hobby, join a gym or a new club, anything to get you focused on something besides your ex.
Get rid of everything in your home that reminds you of your ex. His clothes, photos of him, gifts he may have given you, anything that makes you think of him when you look at it, throw it away or donate it.
Date other people when you are ready. Dating others will help you start thinking about the future, and realize that future doesn't include your ex.
Consult a therapist if the problem persists. Talking to a counselor or licensed professional may give you the tools you need to fully move on.