Having come close to beginning this topic myself, I see that Linda beat me to it. There are already some observations flying around on this subject (see "What is Truth/With Another"). One notes that everyone deals with this issue no matter how old they are; another suggests that even if we age well, it's not due to aging per se, but to something else (Remember, Linda?)
So, in contrast to Linda's previous post, research lately has found that as people age, they do become happier, seemingly as a function of aging itself. While granting that, I still agree with her that there's more to it than meets the researcher's eye.
Retired, I have little money but much time. Often ill (Chronic Fatigue Syndrome), I have choice, which is what time brings, as well as having to learn to focus my mind on what is valuable, and de-focus it on what is not. To my amazement, we really do possess some choice of who we will become, more and more as we develop that capacity. Happiness is a choice within the grasp of most, I've come to believe, and learning to keep poverty and illness at bay has taught me how lucky one can be as one learns to focus one's mind. (William James wrote a century ago that the only free will he could find was in our capacity to direct our attention.)
I live close to the bone, but the remnants of my heretofore middle class life have enabled me to convert my studio into a photography gallery and library. And being poor I've qualified for subsidized housing, so I pay a relatively small rent for a large studio looking out over the City. I'm more interested in learning for learning's sake than ever before. Learning as a teacher was continually pressured, with deadlines and busywork in the background. On the other hand, learning was always socially valuable, for most of what I learned could be put to use in my classes. I always felt as though I was learning for all my students. So there are gains and there are losses.
But I'm also very lucky. Enjoying a temporary decrease in pain and fatigue, I twice recently rode my scooter about an hour out to the Sandy River, where I walked and swam in the cold but not icy currents. It struck me that I was the only aging person out there: beaches filled with families and kids. When I got caught in some rapids, and had to remain oriented with some desperate dipseedoodles, I was again amazed at the core of energy I was able to draw on. I think it was Cicero who wrote that it's good to find the aged in the young, and youth in the aged. And with Einstein, and modified by me: People (need not) grow old no matter how long (they) live. We never cease to stand like curious children before the great Mystery into which we were born."
Aging is full of surprises. In the face of a culture that sees one as little but old, my insides hidden by cultural additudes that don't lead people to expect much inner life, I sing aloud as I walk through Portland's wilderness parks, and delight in all that I'm learning about the American Revolution, the nature of memory, how not to write essays on THINQon, the misery of loss, the preciousness of 30 and 40 year friendships, and so on. Freed from the labors and obligations of midlife--raising a family, creating a career, worrying about one's kids--one is enabled to start yet another chapter, but with no burden of the future to weigh it down. These are the final years, the curve is on the downside, and the days are delicious and unknown.