Some discipline is simply knowing which decision you do not want to remake every day.

Willpower gets spent on repetition. Deciding each morning whether to go, what to eat, or when to stop work costs something every time, and the deciding is frequently harder than the doing. Settling a question once and treating it as closed removes a daily negotiation with yourself, and what looks from outside like discipline is often just a decision somebody stopped reopening.

Find the question you argue with yourself about most often and settle it for a month. Write it down, keep it dull and specific, and let the answer stand on tired mornings.