Squash is far more than hitting a ball against a wall. Every movement, every shot, every tactical decision is governed by the principles of Newtonian mechanics, rotational dynamics, energy conservation, and fluid dynamics. 

Understanding the physics gives you a framework to analyze and improve your game with precision. 'Extend your arm' means 'increase your lever arm to generate greater torque.' 'Bend your knees' means 'lower your center of mass for improved stability.' Every coaching cue has a physics principle behind it. 

Learn the physics. Internalize it through practice. When you can feel Newton's laws and Bernoulli's principle on the court, your squash will reach an entirely new level.