First, you need to stop yourself from checking out your Ex all the time. It doesn't help if you are still connected on social media. If you really need to forget her, then you need to disconnect from her. Delete her from your friend's list. Secondly, try not to think about him/her too much by getting yourself distracted by other important things like work, studies, or travels. Lastly, if you have common friends, try to limit your contact while you are still in the process of getting over your past relationship. If you are really determined, then you will do all of these.