As I see students follow the same beaten path semester after semester, what I (and every other academic instructor in the history of the world) would love for them to realize is that the same concept of specificity governing the improvement of easily visual aspects like musculature and dexterous skill governs mental alacrity as well!
Here are things you hear all too often in a classroom translated to the world of fitness:
This is exactly what students are saying with their various lines. When looked at through the lens of physical progression, you can see just how silly it is. Is math easy? Heck no, not for everyone, not for most. Are you going to have a career in mathematics? Maybe not. That's not really the point though. Critical thinking skills and exposure to the most powerful system man has ever produced is not a bad use of time.
Remember though, when you feel weak on a topic or problem set, that you might actually be weak. Not because you don't have the mental ability, but because it's a heavy weight and you have to work your way to lift it. Keep pounding away and you WILL LIFT IT and it will feel great.