Mine used to be my sig (hey! just noticed we no longer have sigs!)
I used to be disgusted, but now I try to be amused.
Every man dies, but not every man truly lives. - William Wallace
The smallest good deed is better than the best intention. - John Burroughs
The man who is afraid to risk failure seldom has to face success. - John Wooden
The longer and more difficult the ordeal, the deeper the cleansing. - Heinrich Harrer
There are many ways of moving forward, but only one way of standing still. - Franklin Roosevelt
Problems you solve. Circumstances you can do nothing about.
Good. Fast. Cheap. You only get to pick two.
Your perception is your reality.
Casinos weren’t built on ‘winners’.
People want to believe. When they start to believe, they stop thinking.
Being a modern man, when I need a mantra I Google one.
This fits so well with my personal mantra:
When in doubt, try it out!
When it is legal that is. So many times I have hesitated to go somewhere or talk to someone and regretted my decision.
However, peccavi’s mantra is extremely relevant here…
Never heard this one, but I really like it. It’s a compact version of my all time favorite: The Man in the Arena by Teddy Roosevelt.
I also like Thomas Edison’s: “ Opportunity is missed by most people because it is dressed in overalls and looks like work.”
“I am happy. I am peaceful. I am free.”
Because every single day, at some point, if only for a moment, I am each one of those things.
Whatever else comes that may try me, however intense or difficult something may be to me, right NOW, That’s exactly when I like to remind myself.
I use it every day, I’d bet. It’s always soothing.
Stupidity always has a price
My version of this is: Why would you not?
j
If it’s bad, multiply by two. If it’s good, divide by three.
If anything can go wrong, it will.
Which probably explains my other mantra mentioned, upthread.
~VOW
This reminds me of another good one from iconic dogsledder Norman D. Vaughan: “Dream big and dare to fail.”
I am a good man. I am a kind and loving husband. I am smart. I can handle this.
This one seems a bit morbid but I like it:
“When work feels overwhelming remember that you’re going to die.”
“…and then they’ll be sorry!” 
Good thoughts, good words, good deeds.
I’m a Murphy, I can confirm this mantra every week.
Personally I like Samuel Beckett’s quote on this:
“Ever tried. Ever failed. No matter. Try again. Fail again. Fail better.”
I’ve always liked the Webb Wilder Credo: “Work hard, rock hard, eat hard, sleep hard, grow big,
wear glasses if you need 'em!”
Avoid hypocrisy.
A mantra that doubles as a useful non sequitur, from the writings of the late, great, Wesley Willis:
“Fuck with me, and find out.”