How To Make A Man Leave His Girlfriend For You

i know this guy and he has a girlfriend but im in love with him. i like him so much im so crazy about him. but he says he has a girlfriend already and i want to know if anyone is in my same situation and i would like any tips on how i can make a man leave his gf for me. i mean i dont want to do anything iligal or anything. i want him to love me as much as i love him. i know it sounds pretty mean to say that but i can't help it i want him all for myself. i can't believe im actually saying this here but its true, i figure there must be someone who is on the same situation as i am.