Kepler's work habits, though they were certainly productive, were (and would continue to be all his life) a source of some disquiet for him. He was in a state of "permanent repentance about lost time and permanent loss of time through my own fault." He also admitted, "Although I am very industrious, I am the harshest hater of work. But I work for my own thirst of knowledge. I am never lacking an object of my desire, my burning eagerness, to do research on difficult matters." His enthusiasms often went beyond his capacity to carry through on them. "In my eagerness, I talked myself into a lot of things that looked easy, but that were difficult and time-consuming in the carrying-out, because the mind is finer, faster, and quicker than the hand."

— Tycho and Kepler by Kitty Ferguson (35%)