Clocking in tired and doing good work anyway is a quiet superpower most people never train.

Performing well when you feel good is barely a skill, since conditions are doing most of the work. The real capacity is producing something decent on four hours of sleep, at the end of a long week, when nothing in you wants to. Almost nobody practices that on purpose, so almost nobody has it. People who do become the ones a shift gets built around.

Pick the task you would normally postpone until you feel better, and do it tired once this week. Keep the standard, lower the speed. That combination is the part worth training.