"Energy constrained" doesn't mean he lacks sugar, it means his brain isn't letting him do the work anymore because it is in the process of burning out.
Yes, this is my intended meaning. I am a PhD student working on my thesis. After a certain number of hours of doing mathematics or algorithm design, I have to switch to easier tasks like reading papers in a domain I'm familiar with, or documenting code.
While I cannot speak for anyone but myself, my performance on highly challenging tasks is capped at 4-5 hours per day. At that point, it is better for me to switch to lower hanging fruit.
If I am feeling especially inspired, sometimes I'll put in a 12+ hour day of hard work. Rarely, even two or more in a row. But inevitably, I will feel extra burned out in the subsequent days.
While I cannot speak for anyone but myself, my performance on highly challenging tasks is capped at 4-5 hours per day. At that point, it is better for me to switch to lower hanging fruit.
If I am feeling especially inspired, sometimes I'll put in a 12+ hour day of hard work. Rarely, even two or more in a row. But inevitably, I will feel extra burned out in the subsequent days.