It's useful to think of ourselves as having an inner fuel tank, and considering how we function best. Unlike a car, which can have its fuel level depleted down to near empty and then be quickly refilled by a stop at the gas station-- it doesn't always work that way for us humans. I know for myself—things are different now that I'm in my 40s from when I was in my 20s. I used to be able to let my inner-resources get pretty darn depleted and, with a weekend off, I could pop back up to full. Now, it feels more dangerous to allow myself to get too exhausted or spent because it takes longer to refill and replenish.
What do you notice in terms of your own fuel gauge? How low can you let it go, and how do you know when you've reached this point?