I like to play squash. Probably the best advice I have been given is to only give 70% with each shot, and focus all that energy on cleanly hitting the ball. Do it properly at 70% rather than flying in and flailing around at 110% (which is my natural inclination!)
This is more than just a squash tactic. I am at my best when I am calmly dealing with what is in front of me. If I decide to go 110% and expend every ounce of energy in pursuit of one thing, i usually burn out pretty fast.
Life is a juggling act. Keep some energy in store. Keep your head and wits about you. Do things in the correct way.