Personally, I find how I spend my time outside of work has a big impact on how motivated and productive I am at work, regardless of how meaningful my work tasks are. Obviously basic things like sleep, diet, exercise are important, but I have also found that spending too much time on things like video games, streaming shows/movies or social media really leaves me feeling depleted and unfocused during work hours. The more I avoid screens outside of work hours, the more productive I am during work hours when I have to look at a screen.
Another thing I think about a lot is that our own brains and sensory organs change (degrade) over time, so my own subjective experience is probably different in some important ways than it was like 20 years ago. My memory likely isn't good enough to fully capture the differences, so I don't even fully know what it was like to be me in the past.
None of us have even experienced the full range of what humans can experience, so even we don't fully know what it is like to be any given person, we only know what it is like to be ourselves. It is kind of amazing when you think about it.