I like this one a lot. From chapter 6 of Part Four. Howard Roak in Ayn Rand's The Fountainhead:

"Look, Gail" Roark got up, reached out, tore a thick branch off a tree, held it in both hands, one fist closed at each end; then, his wrists and knuckles tensed against the resistance, he bent the branch slowly into an arc.

"Now I can make what I want of it: a bow, a spear, a cane, a railing. That's the meaning of life."

"Your strength?"

"Your work." He tossed the branch aside. "The material the earth offers you and what you make of it…"