I had a wonderful experience playing the whistle the other day. I hit ‘the zone’. I played ‘maid behind the bar’ over and over and over. It was amazing, as if the tune was playing me. I wasn’t thinking about it at all, letting it flow. I was adding in some embellishments here and there and as the tune was playing I was like ‘oh next time that part comes around I’m going to do this, here it comes, then just do it’. Very cool. For the first time , I feel like I know what it means to be a musician.
Gotta love it when that happens. Call it ‘flying fingers’, ‘the zone’, Nirvana, it’s a good thing. Whatever you’ve been doing in terms of learning and practising, it’s working - congrats.
Good for you, and congrats!! Now take a moment to reflect on the circumstances, in the hope that you can find “the zone” more often. For example: what’s going on around you? morning or night? alone or with others? good weather or bad? high or low-stress period? hungry or full? sober or lubricated? new material or old? standing or sitting? lucky shirt? full moon? …etc…
I have thought about these things over the years and have found ways to increase my chances of having a good “play period”. 
Also I’ve learned to recognize when it makes sense not to even approach an instrument. 
You’ve gotta marvel at the pros who can turn it on and off at will. Zen masters, I guess…
From observing and talking with ‘the pros’, I think the biggest thing, after praticing, of course, is not worrying about it, just playing… even the pros make mistakes, and more often than most folks can even begin to notice, but they simply play on, or use the mistep to lead into something a little different but back into the proper spot… or invent something entirely new… it’s all part of the ability to ‘be’ with the music… I dream of ‘being’ that when I grow up…
Welcome to the addiction. 
Me too. Good thing I’m only 53. 
Ah - I know this spot. In fact I live for it (more or less). I used to get this on guitar after parcticing 6 hours/day for 2 years. But only on stage or playing with others. I got a hint of it on whistle at my local session a few nights ago playing The Butterfly - you get to understand why the really good players tend to bop around as they enjoy what they’re doing.