The goal is not to never get tired; it is to stop letting tired make decisions.

Tiredness is real and it is not a character flaw. What causes trouble is granting it authority, letting an exhausted hour decide what you are capable of, what your work is worth, or whether something is still a good idea. Fatigue is a state, not an assessment. It reports accurately on your energy and very badly on everything else.

When you are worn out, restrict yourself to decisions about the next hour and postpone the rest. Rest genuinely, without turning it into a verdict about your ambitions. Whatever looked hopeless at eleven at night deserves a second look after sleep.