Life isn't ends here. It's hard to believe that you have lost your girlfriend. Stay cool and calm; do not perform any such activity that leads to impossible situation to get her back. The probability of getting her back is all how you behave. Meanwhile, control your nerves and behave normally. Few things you really don't need to act upon:

Don't be Desperate. Never be too straight that you can't live without her or beg your love. This will even force her to think that the decision she made was correct. It's not going to be easy at all when you really love someone. Do not propel yourself to make such behavior that ends up all the ways towards her.
Be patient, it will take some time to her but your right endeavors will help you get your girlfriend back. There must have been some reason for which she lefts you. This might take some time to understand what went wrong.

Don't Argue. Keep a tab on your tongue. You need to stay cool and calm at times. Regardless pay some attention and behave in a positive manner which shows your eagerness towards getting your girlfriend back. Keep your pride aside; if you really love your girlfriend, there is no point having pride in between you. Your girlfriend would like to see a change and that too positive, so if you argue, you will be left with no choice rather loosing her.
Don't make Jealous. Never ever try this. If you really think that by showing her more girls around can really make her jealous and think to get back. This is considered to be the most irrelevant point and a stupid act from boyfriend. Even she can do the same but it all differs is how you can keep her happy even she is not with you.
Don't Call or Send Text Frequently. If you did this, after a while, your girlfriend will respond you in utmost way which could certainly be not easy to digest. She will get irritated and throw everything of hers on to you. Calling once or twice will makes her think that you still bother about her but calling 5 times day will kill all your chances of getting her back.

Author's Bio: 

Who knows your girlfriend better than you? Still you don't have clue, how to get your ex back in your arms. Be extra careful and have patience and make sure what you don't have to do to get girlfriend back . Avoid screaming to get my ex back and everything else mentioned above.