Sometimes, boring is as good as it gets.
A child’s life is like a piece of paper on which every person leaves a mark.
How I live my life: Always have plans B through z prepared. Anything could happen at any time. Also be two steps ahead of the curve. It helps to be prepared than unprepared.
Here are some of my other favorites:
Man plans, God laughs ( and I consider myself an agnostic)
Make it a great day or not…the choice is yours
Also a big fan of one already mentioned, Not my monkeys, not my circus.
I’m really enjoying this thread. So much wisdom. All I can add is a helpful bit of advice I was given long ago and has served me very well.
In any negotiation, you owe it to both yourself and the person on the other side of the table to always use the “four F’s”; that is, to be Firm, Fair, Frank, and Friendly.”
Sometimes that can be very difficult, but it goes a long way toward solving problems.
Nike’s “just do it” or as my lab mate used to call it, ITGSD (will not even try to me spell it out. 
).
birthing is hard
and dying is mean-
so get yourself
a little loving
in between.
― Langston Hughes
It’s not really a personal motto, but I have always loved this for its gutsiness:
“They tried to bury us. They didn’t know we were seeds.”
“Drink more water” (which is my favorite thing to say and my kids will probably have that printed on my headstone someday)
And one more:
“it is what it is”
Don’t negotiate with yourself and lose.
From my mother, who died in 1987, “be the better person”.
It’s better to regret what you have done than what you haven’t.
To whom much is given, much is expected (my kid is tired of this one)
My mom’s favorite consolation mantra: Small troubles keep big ones away.
I tortured my kids with this one: Whenever they said, “But I didn’t mean to…” I’d say, “you have to mean NOT to.”
But overall, especially these days, “Be Kind.”
I’m enjoying this thread very much. Thank you!
I haven’t been able to identify a personal motto, so I asked my kids. They remember me saying “Use your thinking brain!” and “Use your powers for good!”.
One kid added, “You were always saying something about poop!” ??? She said I’d say it in response to minor complaints. Along the lines of: “At least it’s not a plate of poop!”
I’m in firm denial, and not sure I want to be remembered for a THAT! 
I don’t necessarily have a motto but I do have a couple of sayings I try to keep in mind.
“Don’t do for someone what they can do for themselves” I use this a lot when deciding how much to do for my children once they reached adulthood. I don’t want to send the message I don’t think they are capable. This comes in when they have to do a task that is hard or uncomfortable.
“Don’t go to the hardware store for bread”
My S says what he remembers most “stay on the trail”.
I use this one almost every day (mostly at work and sometimes at home)
“Do you want to prove you are right or to get this done?”
When you’re a hammer everything can start to look like a nail.
Nap when the baby naps.
“My S says what he remembers most “stay on the trail”.”
We’re not a family that uses a lot of mottos but I did often tell my kids the opposite of the above, at least figuratively, “Don’t be a lemming”. Sometimes good things happen when going off the beaten path. 
I read this one awhile back, and think it was here on CC but don’t know who to credit:
"You can’t keep trouble from coming, but you don’t have to give it a chair to sit on.”
Things are never so bad that they can’t get much, much worse!