Pain comes as you age. It isn’t unique to modern man, other than we typically live longer than ancient man.
If you do this plan you can still cheat. Drink, party, eat whatever. You invest effort so you can enjoy life when the moment arises.
Trying to decide which one to get.
I’ve got the AW Ultra and I’m quite fond of it, ability to use it without carrying my phone (even audible audiobooks) is the killer for me.
Hardware-wise they're largely similar, with some additional edge use cases (depending on who you are ofc) for fitness and outdoors with Garmin.
On the Garmin side for software, one thing I really appreciated on Garmin was the "body battery", or estimate of your energy, as well as health trends, etc. Apple has caught up with many of the features in the last year, and has a little ways to go. Apps like Athlytic do a good job filling the gap, but Apple really is making that gap quite small. Garmin locks your workout data down to its garden somewhat limiting your exports and has it more readily cloud accessible than I'd prefer; I felt the Apple privacy protections were better after reading the TOCs and looking at how the data is stored on each service.
What ultimately made me decide to go with Apple Watch is the above data consideration, the smooth functionality and integration with my iPhone, and the rapid pace of development Apple has had. Also, the cellular, texting (not saying it's the preferred method), Apple pay, etc. are all great to have on the Apple Watch and I can go for a run with only that.
After I paid more attention to my body metrics, I also changed my habits and started focusing on hydration more, when I drank alcohol and how much, and I was able to make good choices that help me feel much better to tackle the next day.
Aside from raw sensor metrics, as someone else said, their Body Battery is pretty decent. The biggest thing for me was seeing a long tail chart for things like sleep score, HRV, average resting heart rate etc and noticing sharp differences on days that I was either sick or drinking alcohol. The effects of a couple of beers on me was similar to COVID (except that they only lasted about 24 hours). But these are things you'll get with any device with long enough battery life that you'll wear it "all the time"
(FWIW, to counter your personal experience with some of my own anecdotal evidence, I always sleep much better on firm mattresses.)
The overwhelming majority of people would benefit from doing resistance training 3x a week, cardio 3x a week, and shifting their diet towards more protein and less carbs and fat. People who fall outside of the large majority due to specific medical conditions need to understand their medical conditions and how they impact their daily life, because expecting everyone else to always take into account these issues is unreasonable and unproductive.
To be frank, this is a dumb point. The morbidly obese person probably can’t even run for 30 seconds. It won’t destroy their joints for the rest of their life. Suggesting activity over inactivity is good advice for basically every human alive.
Suggesting activity is good, yes, but suggesting someone should start with lifting specifically when they have issues with their joints without any further context is moronic.