I describe my personal experience:
In September my boyfriend and I broke up. I thought I was going to get over it soon and that's because he treated me not very well, but the reality is that no, it is not easy. At the beginning I was in the stage of wanting to go back with him, of crying around the corners, it was like I couldn't saw no way out.
Now that we are in April, I am doing much better, but I still cannot say that I have forgotten him, I wish ...
My best friend gave me a really helpful advice, wich is remembering all the bad things he did to me (or, in case he didn't hurt you, remembering all the bad things related with him), instead of remembering the good ones. I promise you it is very useful. It doesn't automatically magically turn the page, but it helps a lot.
In my case, I also have it more difficult, because he is also my classmate, that is, I have to see him every day. But I'm sure it's a matter of time: the longer I go without seeing him and nothing, the sooner I will forget until he falls into oblivion. I think time is the key, but there is no recipe or anything like that. Friends, spending your time on things you like to do, studies and above all, not stalking his social networks, they are things that help a lot too, I wish you the best of luck!