One sided

Why is it so hard to let go something completely. I admitted that one sided love is the most hard to experience...I am experiencing it now.... I like a girl and she alr has a bf.... Y? why am i so slow, if i am one step ahead, i would get her by my side right now.... I hate it when i like a girl, her heart is with someone else.... I really hate the feeling... I thought i let go of her, but why the feeling is coming back now? WHY? i cant take it anymore alr, it is very painful, i cant move on futher in my life where i am stuck at a point....Damn my heart, it is being pierced with a sharp blade.... I really like that person very much, if she has no bf in the first place, i think i would act a differnt way around her..... Damn why am i so slow when it comes to relationships??? WHY? WHY? tell me the main reason why? i cant seems to understand what is the hell going on in me that everytime such one sided love happen to me? Its painful, it is hurtful, it is grieving and it is the most fuck up feeling.... I hope things change when my life goes on and on, things get better and i hope that it will be the lat time i would do this.... Damn the feeling is so strong, even when i am typing this post, i am still thinking of her.....when at outside, i did not look at pretty girls like i always do....... not anymore, this can show how much i am drawn to her.... damn i really wanted time to go back to back, so as to give me a chance to make my move..... I like her!