To get someone back after a breakup might seem like an impossibility especially if she/he has told you that they no longer want to be with you, but I am here to tell you that it is very much possible, in fact it's not hard at all.
The mistakes people make when they want to get back with someone is that they keep calling the person.
Now maybe you've done this, I am here to tell you, IT MAKES YOU SEEM LIKE AN OBSESSED STALKER.
No one wants to be with a stalker.
Choosing to cry and cry will not bring him or her back.
If he/she knows you're crying over them, it will make them feel way too important and you will lose their respect, so even if they come back, they'll act like their doing you a favor and believe me, you don't want to be in a relationship like that.
So, what exactly can you do to get someone back? First off, accept that you've broken up.
Now I know this is a hard step but in order to fix something you must admit something is wrong.
When you are trying to get someone back, you are pretty much trying to build up a brand new relationship because the old one is dead and to do that you must accept that the old one is dead.
Secondly Step: Please don't call your ex when you're still emotionally unstable.
Never call your ex until you have completely accepted the breakup in your mind and have gotten to a good place in your emotional reaction to the event.
You must be stable enough to see them as just a friend or else you'll freak them out and lose them forever.
Third step: After you've gone through all this steps, then you should arrive in a place where you are more calm and rational, and at this time if you still want them back, then it could be love.
Now, you can give them a call, spark a casual conversation, don't talk about your last relationship (remember this is a brand new one).
Don't worry about who was wrong the last time around.
Approach him/her as a friend and be a friend, you'll be surprised that she/he will start falling for you again.
Be very respectful and learn from your past mistakes.