I know you aren't asking the the questions, but since people throw around the term workaholic I'm okay with saying in his case it is pathological. It has been at the expense of his health and family (and it is not for the money because he doesn't make that much, it is for the abuse of the work). But he is aware and has worked incredibly hard for the past eight or so years on that side of his "ism" (he had addict parent) that I am super proud of him. I'd put him at a "normal" level of overachiever now, still saying yes a lot but, more or less, manageable. So we shall see.
Edit: thank you @spartana
I personally don't think there is a "normal" level of overachiever.
There's only a net benefit to your overall well being or a net detriment. For some people, throwing themselves wholly into their work is unquestionably the most beneficial thing for them to do.
The childless, single antarctic researcher who eats, breathes, and sleeps their scientific mission is likely getting a net benefit from throwing everything they have at their career.
Meanwhile, the megacorp employee who is only working 40-50hrs/week, but is a mega people-pleaser with a toxic manager might be totally falling apart in terms of their health, their mental function, their marriage, and their parenting. And for what? They could just get another job, or if they have enough money could just quit.
It's not the level of performance that's the problem for people, it's the unhealthy priorities and boundaries that create problems. I'm just as driven as a I ever was, but thanks to a lot of therapy, my motivating drives and boundaries are much healthier.
I'm even more aggressively ambitious than I was before, but I've redirected my definition of success to reflect my overall health and well being. So it's now easy for me to turn down a work request if I know that it will compronise my ability to take optimal care of myself and my family.
Ambition is a great thing. You will encounter very, very few people as ferociously ambitious as I am. But when people direct their ambition all towards external, professional reward, that's where it becomes dangerous, damaging, and massively inefficient if the goal is to have good outcomes.
Lol, I'll never forget years ago taking my DH for a walk, we were in our early financial and career planning stages. I had been crunching numbers and plotting trajectories for months trying to figure out the most efficient use of resources.
No matter what I hammered out, I kept slamming into the same factor as the largest potential contributor to plan success, and that was if we managed to avoid divorce.
My, at the time, ultra pragmatic, robotic, ice queen self had a "bleep, bloop, bleep" moment where it hit me that it was inefficient to push my career at the expense of my marriage. There was no version of success that wasn't seriously damaged by a divorce.
That was my first moment of major insight that this whole personal life that happened sometimes between work hours was actually just as important.
Years later and work is now something that is a tool to serve my success, it isn't the success itself. I've learned to abandon any and all work that can compromise our overall long term success.
I've identified physical health as a key metric for all possible outcomes, which means that sleep, daily PT, and nutritious food have to come before work obligations. It was a matter of shifting my frame of reference for "success," not reducing my ambition and drive.
Success to me no longer looks like praise from my employer and making more money. It looks like exquisitely straight posture in my 80s, decades of intelligent and funny conversations with my spouse, and work that adds to my overall sense of life richness.
Workaholism isn't a problem of excessive drive, it's a lack of integration of the work self within the whole self.
To everyone I meet, my ambition and aggressive drive are downright palpable. As I said, if anything, I've become even more ambitious since I retired because I no longer have a day job throttling my potential and holding me back. DH often says that my career was just in my way.
Your DH doesn't need any reduction in his level of ambition and drive to over achieve, he just needs a healthier and more integrated sense of self and priorities and then to let it rip, full force in the direction of living his best life.