What should i do ??????????????

i am a 14 year old girl and i am getting attracted to a guy , but i dont want to have any crush because earlier when i used to like some other guy but he does nt liked me i felt very bad n i cried allot and i was nt able to concentrate on my studies so what should i do to keep these stupid thought away from my mind coz my mom told me that in teenage having crushes n all are very obvious but you should concentrate on your studies first ........ so please help and tell me that what should i do to divert my mind from my crush to my studies ?