The Trail Grows Dim
Yes I've had the physical changes, less muscle mass, reading glasses, a larger shoe size, but the most profound thing I've dealt with is that I don't have a firm grasp on who I am.
Along the same lines I don't really know what interests me any more. I've also grown cynical of a lot of things.
I keep working and paying the bills, loving my wife and kids, but I think that somehow if I just keep the machine going, the territory will eventually begin to look familiar again.
If you 'keep on keeping on', the trail will grow more clear, but it might not look familiar, as you may be in new territory. Nevertheless, if you keep your feet moving, you will find your way out of the wilderness.
A book I recommend is "Crossing the Soul's River" by William O. Roberts Jr.