Most of us, for most of our lives, conceptualize work as a linear function. What I mean by "linear" is that the amount of productive output you create is directly proportional to a number of hours you input.
So working two hours will produce twice the results as one hour. And eight hours will produce four times that of two hours.
We all kind of go through life assuming this is the way things work (for the most part). This is mostly because school work functions pretty linearly. They give you a bunch of stuff to memorize, and if you spend two hours memorizing it, you'll remember about twice as much as if you had spent one hour.
Then we get older and stop picking our noses in public and we just assume that the rest of life will function the same way.
But it doesn't.
The truth is that most thoughtful, brain-intensive work does not unfold like this. And this feels really unfair to us. So we spend a lot of time complaining to our parents and making excuses that our bosses don't appreciate our "genius" or whatever.
The only work that is linear is really basic, repetitive stuff. Like hauling bales of hay. Or packing boxes. Or really obnoxious data entry on gigantic spreadsheets. Or operating the fryer at McDonald's.
Four hours is twice as productive as two hours is twice as productive as one and so on.
Sadly, the "work as a linear function" is where all the religion of "Bro, you've just gotta hustle" comes from in the startup world. Since, in their minds, 16 hours of work is twice as productive as eight, the logical conclusion is that you're all just a bunch of lazy sacks of shit, and you should be putting butter in your coffee at 4 AM and coding until your eyeballs bleed. Hustle, hustle, hustle.
As we'll see, as well-intentioned and glamorous as the Religion of Hustle is, it often backfires on people. Because the truth is that most types of work (especially work that will make you some money in 2017) does not produce linear returns, it produces diminishing returns.