Well, I've had a few days to think about it, and perhaps the most astonishing thing about being 50 is how much I feel I haven't changed at all.
Obviously, this is untrue.
Perhaps it is better to say that I have changed, but in far more subtle ways than I could have imagined. The most important of these is a sense of no longer having to prove anything to anybody, but most particularly myself. I simply am.
As for my expectations, enthusiasms, loves, and affections, well, they have been in place for many years now and have not altered except to deepen and broaden. There is strong sense of unbroken continuity in my life now that is internal in nature and cannot be altered by events. This sense of purpose is spiritual in nature, but in a wholly integrated and unobtrusive manner. No need to trumpet what is.
Life's journey has never ceased to be a voyage of discovery. I feel happier today than at any point of my prior life, and really there is nothing more to ask for.