Similar to our physical energy getting depleted, the implication with decision fatigue is that the quality of our decision-making deteriorates with overuse.
Successful people attempt to conserve their “energy” for high-impact decisions, and put less important ones on autopilot.
The trick to doing this is to NOT strive for variation when variation is unnecessary. You decide where variation is necessary. Examples might be dressing consistently (Steve Jobs famously wore the same outfit daily) and prepping a consistent breakfast for the following day (don’t start your day with “what should I eat?”).