Cut off all contact with your ex. Do not correspond in anyway, shape, or form unless until you are over the relationship. So many people (myself included in the past) will try and keep in touch in hopes your ex will want you back. You’re ex is probably just as lonely but don’t give in to their selfish behavior. Seeing your ex again will open new wounds and you will feel worse after corresponding with them.
See your friends. Now is not the time to sit in a room by yourself dwelling over your ex. You need to be around people right now. Your real friends will allow you to lean on them at this time of need. Even if you need to stay over at their place, there is no shame in needing human contact at this time. Go out and have fun…the big caveat here is do not go out looking for a one night stand. This is just a band aid, and you will not feel better long term. However, getting out and being around is important. It takes your mind of the pain and replaces the good memories you have with your ex with new memories with your friends (it sounds cheesy but it works). Also, do not got out and get super drunk after a breakup. Alcohol is a depressant you do not need that right now.
Exercise, exercise, exercise…you have no idea how much this helps. You feel good automatically with endorphins rushing through your body, and you self esteem, which may be somewhat damaged, will receive a tremendous boast after a productive workout. This is a very important activity during this time. Not to mention it worked for Forest Gump, although you do not need to run across the country 3 times to make it work for you.