Never give that type of power to a women. Never be in a relationship unless your ready to leave at any moment. Always have one foot in the door and one foot out.
Now there is no advice on how to deal with it. Use it to learn. Use the pain to make you better and stronger.
Most importantly understand this. If a girl breaks up with you, she actually did it a long time ago, depending on how long you were together. She just finally was able to tell you, but in her mind its been over a while.
Also, when a girl breaks up with you there is no going back. I know in the back of your mind your thinking ''if she just understood me, if I could just talk to her, I can change''. Its over, she either hung onto you until she got another option, or shes banging 5 african gents as we speak. Erase everything about her out of your life. DO NOT CALL/TEXT/EMAIL. this is a sign of weakness and will only push her further away.
I had a girl a little while ago say she didn't want to see me anymore. took me by shock, but I was prepared. I said ''ya I've been feeling the same way, this is a good idea'' hung up the phone. 2 days later she was blowing up my phone trying to get back with me.