If you're doing your best, you won't have any time to worry about failure.

The line contrasts two mental stances: committed effort versus anxious rumination. It suggests that wholehearted engagement in the work at hand crowds out the unproductive habit of rehearsing defeat. “Doing your best” functions as a practical ethic—focus on controllable inputs (preparation, persistence, craft) rather than uncontrollable outcomes (how others judge, luck, timing). The quote’s appeal lies in its motivational reframing: fear of failure is treated not as a problem to solve directly, but as a byproduct that diminishes when attention is redirected to purposeful action. In a narrative context like P.S. I Love You, it can also read as encouragement to keep living actively rather than being immobilized by grief or uncertainty.