Well, I've just done GCSEs got 4As, 5Bs and a C (not great by TSR standards I know)
Basically my advice is, for now, stay on top of homework and coursework but don't do any intense revision because when exam fear kicks in and you are already doing insane hours, you will totally lose motivation.
What I did when it was closer to exams was everytime I was in a good mood but had nothing to do, I would revise. Trust me do this, do not try to revise when you arent in a good mood because nothing happens. That time wasted looking at your textbook you could be watching tv as you won't learn anything.
Revise for all of your mocks so you can see the gaps in your knowledge. I didn't do this and in my January mocks I had a D in biology, C in Chemistry and C in Physics as I hadn't revised. I ended up getting As in all 3 but since I didnt revise I had to work through 900 pages of textbook in like 2 months, along with my other subjects such as pulling a U in ICT up to a B in the last week. If I were to just revise and do coursework on time no joke I could've got 8As out of 10 GCSEs (English Lit&Lang were just never happening for me).
Good luck and chill out but not too much