I'm not in any way calling your dedication or work ethic lacking by what follows:
There are a lot of folks who have spent extended periods putting in 100 hour work weeks and up for years, and all their hours are "hard" hours. When my parents were young medical residents (1970s) for 12,000 dollars a year they ran 117 hour work weeks for their first 2 years. 36 on 12 off, 2 days in a row off every 4 weeks. It stayed above 100 for a very long while, and I can still remember weeks where my dad (a surgeon in a small town) didn't come home for 4-5 days because it was easier to catch a quick shower and a nap at the hospital for an hour or 2 and have our cleaning lady take him new clothes to wear than come home. He probably had a running average of 70-80 hours a week (if you include patient file dictation time of 2 hours every morning, weekend rounds, and weekend ER coverage). I'm sure both of them wished they could zone out for 40 hours, but it doesn't quite work that way (and yes, I'm well aware there are probably many dead or maimed patients because of how doctors like them were trained at the time).
my cousin did M&A/structured finance law at a major firm in the city for several years. I know at least 2 years he billed 3500 hours. If you know much about law in that area, you get to bill no more than 75% of your actual working hours, so he had a couple years averaging near 100 hours including on his vacations.
They aren't the only ones of course, but I think for any of this, until you have actually been given clockable hours and continuous work on a schedule that has you go for 100 hours it's hard to imagine what it does. But I can say that you do learn an incredible amount of mental stamina. You can't learn to run a marathon on only 3 mile outings a day. I think this is similar.