concentration....hmm ....
well thats a prob for many...i'll giv u a small example.... wenevr u watch TV... u watch it with full concentration..y ??? cuz u hav interest in that thing... same goes with studies too.... get ur interest developed in the subjects.... enjoy studies.... dnt study for too long hrs...but watevr u do, enjoy it.... ur concentration will be thr on its own ....
nd yeah, if u want to achieve sth in life, u hav to sacrifice/give up somethings..... so be determined for that!!
gud luck