Two of my favorites are:
"Rome wasn't built in a day, but they laid bricks every hour."
Had a launch day that didn't go as well as I'd hoped. But this quote has been bouncing around in my head, reminding me that constant and focused work will get me there. No matter how small.
"Three foot world."
The only things I can control are within the three feet in front of me, so that's all thats worth my time.