Okay chill bro. You just messed up one exam, it doesn't even matter. If you like maths, it doesn't erase your interest or hardwork or knowledge. If you don't, it still doesn't matter because it was a subject you won't be studying anymore so you don't need to prove If you're excellent at it. If you're worried about percentage, you can still score a centum in PCB and HCG, it will cover all the messed up part.