You don't have to be maxed out on creativity to do good work.
The days when you're at 20% of your best suck. It sucks for everybody.
But you can still grind out some good work.
The challenge is to stop looking at whatever you'd ideally like to do, the full day's work which can often seem near impossible when you're flat.
Instead, just chip one thing off.
Got a stack of 10 things to do?
Just commit to getting the first one done and focus on that.
You'll rarely have one of your best days if you start out down around 20% of max energy for whatever reason, but you can have a surprisingly productive day if you chip away.