Me too, and I'm doing a-levels. But a few months ago I was thinking that a capital letter won't make me happy, when I'm on my death bed I won't be "ahh remember the time I got a B in a-level biology, so happy I put myself through two years of misery and sleepless nights".
As long as you get your maths, English and science you'll be set for life, and if you don't it's not the end of the road. So much out there that's better and no grades are required.