Well said. I think the mental aspect has a lot to do with it. I can think of times when I excelled, and there was a certain stillness of thought, that somehow enhanced the execution of the prior fundamentals that have been learned and adhered to. If everything is right anything can happen, but, as you mention, with no consistency whatsoever. Usually, after a long hiatus, it can be mediocre or worse.
Another example from when I was a golf nut, one year the best round I scored was the first outing of the year, that was a good day for some reason. Have no good explanation for it.