Really enjoyed reading this thread.
"If there is nothing to do, do nothing" - sounds simple, harder in practice. It is definetly cheaper and more productive to go to the gym or take a break, when the market is in a quiet time. No point driving yourself nuts in the interim.
other one I like is "Quality, not Quantity"
Doing fewer trades but with a higher winning percentage enables you to trade bigger size more confidently.
Also, I think there is a limit to the number of "good" decisions you can make in a day before you get tired/slack. Some days maybe a handfull, others just one or none.
So even if the trades are there but you feel you are falling behind, leave it.