There is a common turn of phrase used so simply, that it is rarely recognized as an insult, until you receive it.
"You're too young to have those kinds of problems." - Really?! Thanks, I'll let my chronic condition know!
Is there ever any appropriate age? No. We are all in this together. The sooner everyone realizes it, the better! Old or young matters not to biology. Each of us has our own path and our own rate of degradation or balance, and there is no standard by which that can be measured. The variables are infinite.
As we come into the holiday season, don't overextend. Be kind to your body and your soul. Take extra time when you need it, stay home when you need it, and ask for help. If your life is such that you can't take the break you need, plan time for yourself each night, where you can devote at least 1 hour to something that brings you joy.
We are ALL, "To young for this.".