Tommy - I've never been any good (took the game up very late, and didn't play much at all for years, and in that context I am still getting better), and so I have no experience with (or insight into) what you're experiencing, i.e. the once very good player who feels that his skills are diminishing. But, I've experienced 'change' in other areas, and -- apologies for getting all airy-fairy and mamby pamby on you, but -- here are three short quotes that I think are relevant.
"We must be willing to let go of the life we have planned, so as to accept the life that is waiting for us."
Joseph Campbell
"What we try to keep for ourselves is just what we are sure to lose."
C.S. Lewis
"We find by losing. We hold fast by letting go. We become something new by ceasing to be something old. This seems to be close to the heart of the mystery."
Frederick Buechner
I know, I know - who wants all this mumbo-jumbo? I just want to hit the ball longer and straighter and more consistently, and putt like Crenshaw in his prime and be as comfortable in a bunker as Gary Player. But if there is one sport in which these kinds of quote 'make sense', I think it's golf.
Best
Peter