I also read that section and thought it unfortunate the author missed that realization as being the likely root cause. External validation seems to be a major driver of his unhappiness. There's nothing wrong with finding solace in structured work but I think if he returns to his old job he's likely to reach burn out unless he can identify this as a root cause.

I made that connection for myself as I've had a strangely similar recent experience to his, albeit without the Amazon warehouse job. I burned out, took multiple months off of work, didn't implement any lasting structures, and became depressed. But I did spend a ton of time in therapy to evaluate my mental health and what drove me to burn out. Practicing self-awareness and emotional awareness has made me more optimistic about finding routines and habits which will bring more fulfillment.