When faced with new tasks, the issue of stamina comes up. For already studied and embedded routines, stamina is not as much of an issue because so much of what those routines include are on autopilot thus requiring less stamina. New tasks, however, require a lot of new learning, changing routines, and problem solving so new tasks often require greater stamina.
I thought about this as I embarked on a number of new routines and found myself quite exhausted. When we are forwarding new routines, we have to give ourselves the extra time we need to get the extra rest needed. The same is true in any discipline when people are engaging in new work and learning--while that novelty is often invigorating, it is also tiring.
To optimize energy for any task requires analyzing just what it takes to do that task well, and that will certainly include some added rest so you can build greater stamina over time.