I think I know what you mean. I'm good at GCSE maths but now I've done a A level exam early I found it extremely hard. I'm convinced I'll get a F. I think that you can easily do the space maths is because you can apply it practically such as calculating the detla V but normal maths is too abstract and you can't apply it to anything. My Physics and recent, forced, A level maths teacher has the same feeling.