This is honest advice and the truth really.
Don't give up your social life etc to do nothing but work for GCSE's because in truth they are not that hard (for most people) and they are merely a stepping stone to A-Level, and once you get into doing A-Levels they barely even matter any more.
Have fun during your GCSE years, because once you get to A-Level, for people who take things seriously, all fun and most of your social life goes out the window.
Yes GCSEs matter now in terms of getting into A-levels or other courses, but don't revolve your life around them. Go out with your friends and have fun. Do your homeworks when you need to and revise when you need to, not obsessively, and you will be perfectly fine.
Don't go out buying every revision guide out there either, because the truth is, you probably wont need them as for the most part everything you need is taught or given to you in class.