Work should be measured by what changed, not how tired everyone became.

Fatigue is a poor unit of account. What should be counted is the difference between the state of things before and after, and that number is frequently unrelated to how much anyone suffered getting there. Measuring by exhaustion rewards the wrong behaviour and hides the wrong problems.

When reviewing a project, ask what changed rather than how hard it was. If the answer is small relative to the effort, look at the process rather than at the people.