Equazcion----"Failure comes with its own lasting pain; the pain of not getting what you want. But that pain originates from the outside. There is nothing you can do about it now, but you did try. You were just dealt a bad hand. That can not compare with the pain of regret, because regret comes from within. It's a self-punishment, it's kicking yourself for not at least trying when you could, and there is no one to blame but yourself. I can think of nothing more tragic."

I feel your pain. You've made your decision to try. While it's different for everyone, the odds aren't in your favour because she has a boyfriend. I was in a similar situation. I made the choice to "get it over and done with" because I didn't want to deal with regret. So I told the person how I felt. In the end the answer was still a NO. With that came immense pain...tortured thoughts....and what I likened to being a sledgehammer to my heart. Inside you are bleeding, and you have to deal with it. With rejection I felt as if my whole being was nailed to the wall for all and him to see.
Looking back, the use of logical actions was no cure for emotions.