Full disclosure: I haven't read the book myself. Logically, however, expressing regrets does not say anything about whether a specific course of action is better. By definition, one can only regret living one's life in a certain way if one actually did - so perhaps a high incidence of people regretting "working too hard" is simply indicative of working a lot being the most common experience, rather than any special reason why a life spent working should be regrettable.

And back to Gregg - he's personally been an inspiration to me. Who would I be to question his life choices, but I for one am grateful for the path he did choose to take.

I think that is a misrepresentation of what the parent was saying. OP is not suggesting everyones gets to do what makes them happy, but rather they are free to say what is important for their happiness, even if others disagree.

This seems like a misreading of the comment. Anyone can choose for themself what matters to them, which is a different question from to what extent you can get everything you want without compromises.