I've been hitting that a little bit later.
I've crossed the half-century mark and this is where I've been noticing some changes. Thing is, when I was in my early-40s I went through a significant life change by way of going through divorce. I actually got a brand new lease on life through that. So, I went through this epic experience of joy, new found things in life, had some new relationships, new friends, etc. Yes, there were definitely negative aspects of it, as I have kids and my heart was sore for them. But we've come through it, thanks be to God and Him alone.
I married 5/6 years ago and have settled back in to day-to-day life, but in a different kind of mode, I guess. I have found that the most important thing in regards to what you are saying, is that I MUST.... MUST... exercise, and I mean regularly.
I've always been a trim person. I've always been able to eat whatever I want and as much as I like. For the first time in my life (seriously) I have started developing some fat around my waist line. If I don't work out and walk, this is what happens. My body is definitely changing. I think that transcends to us, psychologically as well.
Seeing your kids grow up and move on in their lives, that too will bring about a spiritual and psychological change. You get a more clear and vivid picture presented to you in living color, every moment of every day, as to what is truly important in life, and it ain't your doggone job... not anymore, at least (for me).