It is very possible to get an ex back. But for that to happen you have to be able to get through why you broke up in the first place. You have to have grown and learned about what you need want and expect out of the relationship. When reconnecting with an ex, it is not about getting back your old relationship, but starting a brand new one. If you go back to what you had, then it will end again.
You also have to make sure that the reason you want your ex back is not because you feel rejected and want to know that you could have them if you want them. That is a waste of your time and theirs.
That is why I think that it is very important to spend time alone after a breakup. It will give you the time to think clearly and know what it is that you really want.