Back to the original topic, if 63 is considered a Senior Citizen I learned at that age that I was "living to work" rather than "working to live". After I retired, I realized that my career no longer fueled me or provided a life balance and that I was happy to no longer be beholden to a particular schedule or boss. I talked to a friend (and former employee) today who retired last year. Neither of us could believe how we had the time to keep up our households prior to retirement. Experts talk about "being in the moment", and I never was while working. Now I notice things like birds chirping or trees that have new sprouts.
At 65, I think about death vs. longevity. I've seen so many of the people who were part of my youth (David Crosby, Ray Liotta, Kirstie Alley, Olivia Newton-John, Christine McVie, Tony Dow, William Hurt) pass away and it reminds me of my mortality. On the other hand, I wonder if I will live another 30 years due to modern science and outlive my savings. That has been the biggest eye-opener for me as a Senior Citizen.