It has been said that three fourths of the break ups are initiated by women
. Women can be a little more emotional than men and say or do things they really do not mean. They may really not want to break up but sometimes they do it to make a point. It's how the guy responds to this that will help determine if he can get his ex girlfriend back.
If you think this is your situation and your girlfriend has left you, be careful that you don't do the wrong things and ruin the chance of getting her back. Your first step is let her have her space, do not contact her. She is upset about something so let her get through that on her own. In fact she may call you within this period of time.
She may sit home and miss those things that the two of you did together and may call you wanting to come back. It may not be easy for her, so be casual about it with her. But understand that by maintaining your silence you are sending her a signal that you are doing ok without her. She will have to decide if she is really ready to move on without you, so hang in there and wait for her to make the first move.
If a week or so has gone by and she has not called you, you will need to initiate it. Try emailing her and casually ask how things are going with her. Make your note look like you are just talking to a friend. If that does not help, try contacting her by text or her facebook page. You can even call her once a week to keep casual communication open between you.
If you know were she hangs out you could show up there occasionally. Don't bug her but acknowledging her is ok. Don't forget her birthday; make sure you send her a card so she knows you are thinking about her. Hopefully she will remember why she was with you in the first place and come to her senses so have patience and see what happens. Also be prepared to move on yourself if she decides to go a different direction.