Getting old and gaining/losing weight

 "Fate leads the willing and drags along the reluctant." - Lucius Annaeus Seneca

Keto Flu

 "It's not that we have little time, but more that we waste a good deal of it." - Lucius Annaeus Seneca

There is another (non-stoic) quote along similar lines:

"Youth is wasted on the young" - George Bernard Shaw, American Playwright

In other words, youth have no frame of reference other than being young, and when you are young, you have a lot of unencumbered free time.  Therefore young people don't appreciate their health, stamina, freedom from demands, and lack of pain.  They have not yet experienced the loss of abilities, overwhelming obligations, and the fragility that come with age.  They (we!!!) don't appreciate the perks of being young.

Exercise and fitness

I'm now a ways on the wrong side of 50 years old.   I've been weight training and doing light cardio for a few months now.  Progress is... not bad!  But it's also a bit slower than what I've experienced in the past.