I feel tired after studying calculus but I can still do it if I try really hard. When I study discrete math or lineal algebra I don't feel as tired and can stud

I feel tired after studying calculus but I can still do it if I try really hard. When I study discrete math or lineal algebra I don't feel as tired and can study for longer. Naturally, I'm much better at discrete math than I am at calculus. I expect extroverted people are better at socializing than introverted people for similar reasons. Are there many introverted politicians?