I tend to overthink things, especially about riding. So Bautieri's phrase "just ride bikes" is something I sometimes repeat.
Some others:
"Weighing 400 pounds was a living death. Now I live every day." - "The Historian" on Bike Forums. :-)
"I have always been of the opinion that, of the two evils - under-estimation and over-estimation of one's own strength- the former is much the more harmful." - Grandmaster Mikhail Tal, World Champion
Presume not that I am the thing I was;
For God doth know, so shall the world perceive,
That I have turn'd away my former self...." - Henry IV part II, by William Shakespeare.
"WWSD - What Would Sayre Do?" - a few people I know on Bike Forums.