If you have lost your girlfriend and now she is nothing but an ex, you have to try to analyze all the things that happened between you two and what went wrong. You must look back and be conscious of what mistakes you did and what had to be different. Many people start to look for their ex without knowing very well what happened and what they have to change. It will be pretty hard for you to convince her to get back to you if you don’t know for sure what exactly happened to you.

I am sure that you already know the fact that many people end their relationship for different reasons. I am also sure that you know that every relationship in the world is not the same with another. You must be able to analyze all the things from your relationship to find out what exactly happened between you too if you want to win her back.
Different approaches in different problems
I will give you one example: if your girlfriend is now an ex because the relation between you two got a little stale you must ask what could you have done to keep the relationship alive and the fire burning between you. I am sure that the things were very nice and romantic at the beginning of the relationship but you got lazy soon after that and you do nothing special to keep her excited.
If something like that happened to you and to your girl, you must think of a way to met her again and do all those dates that you missed romantic and full of love. You must try to show her how much you love her and that you still have interest on her. You must try to spice up things and you must be creative because you need to plan a lot of activities in order for you two to have fun. You must try to avoid the monotony in your relationship because it doesn’t bring good things.
If your relationship is over because you were cheating her with another woman, you must do anything that you can to show her that she can trust you again. You must try to explain her as best as you can what you did that and that you learned your lesson and you will never do it again. You need to do anything that you can and that it’s in your power to regain her and all of her trust. Keep in mind that trust is an important thing in a relationship. You can try to offer her your sincere friendship.
Different problems need different ways to be solved. If you look in the past you will notice little clues left by her telling you that she will be soon gone. You must remember all those clues and consider them as much as you can. You need a plan and you also need to stick with it!