Concentrate on yourself. As weird as it sounds, be selfish for a little while. Do things you want to do. Go places you want to go. If something doesn't sound like fun to you, don't do it. Join a group. Volunteer. Concentrate on a new hobby. Anything really, as long as you enjoy it to the point that it keeps your brain focused on it.
Don't dwell on your ex. If you start to think about her, just move on to something else. And recognize that you are no longer together for a reason. You can learn from it and move forward.
Good luck.
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