You've heard it before, just get your head down and push through. Is that really the best way to get things done? Study after study has proven the value a rest breaks. Efficiency drops if you push past peak efficiency.
Here's an illustration from my own experience.
The Iron Butt Association (yes, that's a real thing) certifies long distance rides. I decided to do a Saddle Sore 1000. That's 1000 miles in 24 hours.
To prepare for the ride, I asked for advice from more experienced riders. Most gave advice on what to bring or how to prepare. One rider shared what turned out to be the best gem that has proven invaluable on many successful and enjoyable trips. Dan advised me to stop for a break every 100 miles. By taking a break BEFORE I got tired it took much less time to recover and be in good shape for the next leg. I have ridden long days many times. When going out riding for the day I'm not very intentional about breaks. I usually just keep going until I get to a destination or need a break. On those days, I find that I'm totally wiped out when I get home.
Oh, and yes, I earned the SS1K certification!
The lesson here is this: take a break before you feel like you need one to maintain top efficiency and you'll get better quality work done more quickly!