A good arrangement does not rely on one person always finding a little more energy.

Many arrangements look like they work when in fact one person is absorbing the difference. The rota, the household, the team, the plan for a relative’s care: on paper it balances, and in practice somebody quietly does the extra bit every time so the gap never becomes visible. That is not a stable design, it is borrowing against one person.

Look at something you are part of and ask what happens if the most reliable person simply does the agreed amount. If the answer is that it falls apart, the design needs changing rather than that person needing more stamina.