Hey zahid. I'm really sorry to hear what happened to you. Nobody ever wants to be in that situation. When you said you felt that she was the one, I knew it's going to be a big problem to overcome her. During this moment, just focus on yourself. Just keep in mind that it is not fair for you to keep thinking about her while she is not (or barely) thinking about you because she is happy with the other guy. It's never fair that way. Acceptance that she is gone will take a long time. Just brace yourself for the journey. Do not get involved with other people yet. Make yourself whole again. That is probably the hardest part, dealing with the pain your self. But just know that there is an expiry date for that suffering of yours.