Mathematics

Math lays the foundation of how to think outside the box. Why do we mess with x, y, z? These help you to think hypotheticals. Secondly it builds confidence in unknowns. You see an equation like something you are familiar with but it poses a challenge. It gives you composure to rely on yourself even when faced with something foreign. It also conditions you to pay attention to detail because carrying out the wrong formula or adding a negative sign can change an answer.
Obviously there are quantitative functions for math as well, to explain something or to explain something more discrete. Some people just remember patters, and simply just memorize 'when I see this, I do that': math is beyond this. Don't take math lightly or it will condition how you think, it will influence your behavior beyond symbols and numbers.

Courses:

Statistics
Algebra
Precalculus Algebra
Trigonometry
Calculus
Differential Equations
The World! - just kidding, calculus and differential is like the math or real life as long as you can find the variables and models to match what you observe (moma nature isnt gonna give you her crib notes)