I don’t have a motto, but I do have some rules:
-Never refuse free pizza.
-Take it easy.
-If it seems like a bad idea don’t do it!
-Every rule above has exceptions.
I add new rules whenever I think it’s appropriate.
I don’t even have a damn glass!
I think it was Eddie Izzard who said
“Some say the glass is half empty. Some say the glass is half full. But, the world belongs to those who say ‘This is not my glass! My glass was completely full! And it was a bigger glass!’.”
Don’t be afraid to get it right
Life sucks, then you die.
Unofficial Marine Corps motto:
Never stand when you can sit; never sit when you can lie down and never stay awake when you can sleep.
“When you point a finger at someone, four more point back at you.”
Which isn’t strictly true depending on what finger does said pointing, but you all get the gist. 
Don’t get caught.
― William W. Purkey
Trust your instincts.
Be prepared.
It was Pratchett, actually. In The Truth.
From Jane Haddam: “In my day, we didn’t have self-esteem, we had self-respect, and no more of it than we had earned.”
From Marie Curie: “Nothing in life is to be feared, only to be understood.”
And finally, “What is, is.”
Treat others as I expect to be treated.
Honey, I would have thought yours was “I don’t give a shit”.
I couldn’t stand it. I fixed it. 
The universe is neither malign nor benign. — Harlan Ellison
I’ll never get out of this world alive. — Hank Williams
Mine is related to video games (surprise! ;-):
That which does not kill me merely fills my Limit Gauge.
And when it’s full I can use my special attack. 
My only fear is that my special attack is something lame like Procrastination. Sigh.
Live only your own life.
“It is what it is”
and
“If you don’t look out for number 1, you’ll step in number 2”
Nothing in life worth having is ever obtained easily.