I'm a car guy, so a lot of my phrases relate to that.
Car designer Colin Chapman is famous for saying something like "simplify, and add lightness" regarding sports car design. But, my favorite take on that is that he also is known to have said "keep adding lightness until something breaks, then put some back!"
One phrase that I coined myself that became very common in my local autocross club came from a day when a friend of mine was out trying to learn his new single-seat formula car. I'd never driven the car, but I knew the previous owner, and I knew how fast the car was... and he was nowhere near what the car could do because he'd never driven anything with the kind of grip this car had. Simply not driving it hard enough, not even close. So, as he rolled up to the start line, he asked me what he needed to do to go faster, and I told him, "Scott, here's what I want you to do. I want you to go out there, push harder and suck less!" So, the phrase "push harder, suck less" lived on. Scott even put it on a plaque on the dashboard of that car!
Another one I've come up with that I use on my driving students (I'm a driving instructor) is Loren's Two Rules of Driving:
Rule #1: People are stupid, expect it. If you're always expecting every person you see on the road to do the dumbest thing you can imagine, then you've always got plan B in your head, and you're ready for anything.
Rule #2: Don't be stupid! Think of all the things other drivers do that make you crazy. Don't be that guy.
Two simple rules, the world would be a happier place if everyone lived by them.
"There are no surprises in this world if you're thinking far enough ahead." - Another one that I tell my driving students, but it applies to so much more than that.
"If you can't go fast on 90 horsepower, 900 won't help you." - Michael Jordan (Automobile Magazine)
"It's more fun to drive a slow car fast than to drive a fast car slow."
"Straights are for fast cars, curves are for fast drivers."
"It's not how fast you go, it's how little you slow down."
"Racing makes heroin addiction look like a vague wish for something salty." - Peter Egan (Road & Track Magazine)
"If one oversteps the bounds of moderation, the greatest pleasures cease to please." - Epictetus
"Beware the fury of a patient man." - Publilius Syrus
Another set of rules:
Rule #1: Don't sweat the small stuff.
Rule #2: It's all small stuff.
Variant of above:
Don't sweat the petty things.
Don't pet sweaty things.
"If you can't find the time to do it right the first time, how will you ever find the time to do it again?"
"That which does not kill us makes us stronger." - Friedrich Nietzsche
My wife's favorite related to the chaos of the workplace:
"Not my circus, not my monkeys."
"We do the difficult while you wait, the impossible takes a little longer."