I worked three years full time and now on a startup. I've come to realize that most of the performance improvement for me with the latter is attributable to a difference in sleep duration and quality. I'm someone who needs variability (+/- 2-3 hrs) in when I go to sleep and little to none in total duration. This is especially important when you're exercising consistently (and doubly so for HIIT).

Work life normally doesn't account for sleep, but I feel like it may very well be all the reason for the problems we see. It's no secret that most Americans are experiencing chronic sleep deprivation. And that's linked to a host of other issues like obesity, learning impairment, low energy/productivity, increased stress, etc. In other words, it has a cascading effect on everything else. Most people need around 8 hours per night to function normally and get only around 6.