> Long hours: "It's 5 o'clock and I should be done with work, but I just need to finish this problem, just one more try," you tell yourself. But being tired it actually takes you another three hours to solve. The next day you go to work tired and unfocused.

> Shorter hours: "It's 5 o'clock and I wish I had this fixed, but I guess I'll try tomorrow morning." The next morning, refreshed, you solve the problem in 10 minutes.

I have too much experience with this. I remember when I was self-employed I humble-brag tweeted about my production deployment ~15 minutes after starting work. A friend of mine asked why I hadn't just deployed last night and the quote above was my first thought (in addition to the fact that you should never deploy to prod then go to bed). I was done with work, so I stopped. It avoids hitting that "grind it out" phase where you're lucky just not to do more harm than good.