How should I win her back?

The most stupid thing I have ever done in my life is letting go of the person I love the most. I had been so preoccupied with my work that I forgot I had someone waiting for me to come home. My girlfriend was fed up and left me with no second thoughts. I let her because I always believe that if you love the person, her happiness becomes your happiness too. Then, I realized that the idea is absurd. It should have been, if you really love her, you won’t let her go and you will fight for her. Those are the things I wish I did way back. When I met her yesterday at a foreign social, I realized I am still in love with her. I asked one of our common friends if she has been seeing someone lately. She said she did not notice anything, so I guess she’s still available. I wish I’m not too late; but how should I win in her back? Advice, please!

The only thing you can do is tell her how you feel.

Arrange a meeting and tell her how you feel. If you love her, then this should not be a question. Do it!

Don't come on too strong off the top. If she left you and had a good reason for doing so, she won't be too keen on grand declarations of your love. Women like consistency over time more than big gestures. Try talking to her first and see if she's open to communication in general. If she wants you back, your conversations will naturally flow towards reconciliation without you having to push too much.

Trying to get an ex back is not for the faint of heart, though. Make sure you are in a place of emotional stability and together enough that you're certain the relationship is worth having back if you succeed. Also keep in mind that breakups change people. She may not be the same girl you were with before.

Unfortunately you can't "fight for" something that takes the consent and consensus of both people. Nor can you "win" something that is about two people and their individual feelings. This unilateral thinking is why she left in the first place. Often breakup regrets are about a little too little, a little too late. Learn from this for the next time, she's been thinking and probably talking to you about this for a while, now she's done.

I had been so preoccupied with my work that I forgot I had someone waiting for me to come home. My girlfriend was fed up and left me with no second thoughts.

At the risk of sounding cynical, here's yet another guy who didn't realize how much he loved his girlfriend until she left him. I swear it's becoming an epidemic round here.

To the OP, can you explain why or how you failed to realize how much you loved her while you were with her, and why it took her leaving for you to realize it?

I don't mean to give you a hard time, I know you're hurting and I'm sorry but women don't experience this, and I hear of this happening so often with guys, and none of those I've asked seem to be able to give an answer that makes any sense.

Also, what makes you so sure that if she were to want to get back together, the same feelings you had when you were together (that caused you to not appreciate her and/or treat her poorly) won't happen again?

Have you thought about this at all?