Studying like madddd~

Yo, didn't post for quite sometime. Have been studying since last week but i still feel that there is more to revise on, but i just don't know what to do, studying Science since last week all the way till not, but i still feel empty, no idea why.. Hope i can things right before my Prelims come and get me. why is my brain like that so stubborn, don't want to throw away those rubbish and stall some useful things ... SAD!!!