You cannot step twice into the same river.
Classical, rich in its simplicity, this is one of the great metaphors. Part of the value I find in reflecting on it is, that even in the abstract, my response is in part assent (the water I stepped into yesterday has long since flowed on into the sea) and in part dissent (the water today is different, is fresh, but it's the same old river that has flowed here for centuries).
Any music-lover of many years must experience, to some degree, at one time or other, a specific variety of disappointment. (I'll be a little circuitous getting there.)
Some music, the first time we hear it, we dislike immediately (or, perhaps, believe immediately that we dislike). Some music, on an initial hearing, leaves us tepid — yet later, on 'absorption' of the piece, we grow into a keen enthusiasm for it. (And let me note that one can grow into a k. e., too, for music one initially disliked.)
All of us, probably, have some pieces (a large handful, even — and the larger, the better) which set our souls afire the very first time we heard it. The specific disappointment mentioned earlier, is related to this class of music.
That inaugural, soul-igniting listen to a piece of music, is an experience which indeed makes us glow. It seems natural for us to want to relive that experience again (and again), yet re-creating that experience is sometimes not so simple as listening to the same piece again. It's a river we cannot step into again. Or, not as a result simply of our will and desire, anyway.
A practicing musician necessarily (meseems) lives through such an experience with many pieces over decades. (I hope so, in all events: I should want all my colleagues to be driven, in part, by the spontaneous, all-consuming admiration for examples of the art.) Probably one's reflection upon and response to this phenomenon vary according to character and temperament.
Now, I began this train of thought by speaking of disappointment. When one has experienced a sort of sonic brilliance on first acquaintance with a piece, if that brilliance seem to fade on subsequent encounters with the piece . . . a type of disappointment seems natural. But it needn't be, nor should be, the end.
One's experience of a given piece of music is not anything etched in stone; it's a river, and the surface of the river looks unchanging but it's always fresh water.
For myself, there are pieces which I heard (and pieces which I was in an ensemble playing) as a teenager, and I fancy I can still now perceive the echo of the fresh excitement I felt then; but at present, I don't think it fair to say that the music has 'staled', but my response to the piece has certainly become sober.
I actually find, over time, that I have an ever-expanding 'library' of pieces which preserve their Excitement Quotient with eye-opening reliability. There must, I suppose, be some subtle adjustment of internal expectation (of the general experience, not of the particular piece, I mean), and the excitement is no whit less genuine.
Perhaps I have learnt a kind of 'renewable musical excitement' framework? It is hardly a matter whose depths I expect to plumb.