Law of Non-Contradiction

¬(p ∧ ¬p)
In plain terms, if P is true, P cannot also be false meaning it is a contradiction.

Why is this important?
Let's say we want to achieve a high grade in Physics. If the best way to achieve a high grade in Physics is to study then not studying with the expectation to achieve a high grade in Physics is necessarily going to fail in achieving the desired outcome.

To state the obvious, studying and achieving a high grade and not studying and achieving a high grade cannot both be ways of achieving high grades.