Holiday divides the book into mind, soul and body, and in each part strings together anecdotes about historical figures to support a stoic virtue. It works as reading and does not survive examination: the examples were chosen after the conclusion, which is the vice of the entire genre.
What I took from it
One idea, and it was enough to justify the read: a decision made while agitated is worse than the same decision made a day later. Not original, and the book does not claim otherwise, but it is well argued through the case of correspondence left to sit — a good share of urgent matters resolve themselves or change shape while you are not answering.
I turned it into two rules. First: no disagreement with a client gets answered the same day it arrives, unless something is down. Second: scope does not get fixed inside a meeting, however much pressure is in the room; it gets written afterwards and sent. Both have saved me from commitments I would have had to break, and both are easier to hold in writing than out loud.
The other thing I keep is the distinction between being still and being passive. It matters for anyone working alone: filling the calendar is the most comfortable way of deciding nothing.
What I left out
Most of it. The body section is generic self-help about routines and rest, and the soul section leans on a blend of stoicism and Buddhism that gets quoted more than it gets explained. The first book in the trilogy says nearly the same thing with less padding, and anyone reading only one should read that one.