How we cite our quotes:
Quote #1
I frequently ride out and take the air;—though sometimes, to my shame be it spoken, I take somewhat longer journeys than what a wise man would think altogether right.—But the truth is,—I am not a wise man;—and besides am a mortal of so little consequence in the world, it is not much matter what I do; so I seldom fret or fume at all about it: (1.8.1)
Tristram is in on the joke. He admits here that he has his own hobby-horse and that he doesn't always act wisely when pursuing it. This is a good articulation of Shandyism: "it is not much matter what I do; so I seldome fret or fume at all about it." We can get down with that philosophy.
Quote #2
He chose rather to join in the laugh against himself (1.10.8)
Tristram describes Yorick's attitude towards his own folly, which is shockingly similar to Tristram's and, we bet, Sterne's—he laughs at it. This seems to be the right approach throughout the novel, and probably for life: better to laugh with than be laughed at.
Quote #3
"would be the most grave or serious of mortal men for days and weeks together;—but he was an enemy to the affectation of it, and declared open war against it, only as it appeared a cloak for ignorance, or for folly" (1.11.6)
Yorick hates seriousness not for itself but because people use it to hide their foolishness (folly). He wants everyone to celebrate folly and enjoy being foolish—basically, the class clown of the novel.