i used to have a super resource person for these things but for now im trying to grow up and learn these things myself - haha! anyway, here's my problem, when im using my MBP and its not plugged in, it just shuts down without any warning even if the battery says there's still 53 minutes. is this normal? should i be worried? is there something im supposed to be doing? is there something im not doing right? haha...yeah im a panicky one. help!