I've seen old tired people (mostly outside europe) so often that it does make me wonder - how will my own life look like once I'm old ...

Everything depends on you, as long as you maintain joy and desire to live that tiredness is never seen (appears). I know very old people who are always doing chores, like my dad, they never see the tiredness of life ... Because they came to live it and enjoy it.

Maybe they are a generation that is disappearing...