How to completely forget a girl that you love the most help please?

please help ths girl i love the most we used to talk alot and she was fond of me she always wanted to talk to me and ive been loving her for 2 years please help me i love this girls more than everything and she love someone else whenever i see her talking to guysfriends or when she look at someone i feel like someone stabs me in my heart i goo soo sad when i go to facebook and see boys talking to her or posting songs for her i feel dying inside please i know theres no hope that she would love me cause i know she will never ever love me back so please give me advice help me i wanna forget her please i wanna forget her and live my life