I experienced this when I first started learning the piano. When I played the first song I had learned for my sister, she was amazed. "Wow, I could never play like that", she said, "my fingers don't work that way". But when I broke down for her exactly how I'd learned it -- by breaking the song down into manageable chunks of just a few notes each, practicing each chunk with each hand separately many times until profi…
Yes, which piece was that btw? I'm learning Rachmaninoff's Prelude in G minor, probably the hardest piece for me to date. I'm not timing the process but this must have been going on for six months by now. Practice occurs only when I feel like it, as I walk past the keyboard. Sometimes less than 5 minutes per day. Rarely more than 15 minutes. But it's getting there! If you added it all up, it would be a tremendous amo…
For me, it's been more obvious with piano as it's my main skill-based hobby and, although I see similar with work, ultimately I need a job to get paid so even if I'm procrastinating over a boring task, at some point that kicks in to make me get on with it.
With piano, I'm only doing it for fun and there are so many pieces out there to learn, so if I realise I don't love a piece then I've now taken to stopping with it after a certain amount of time. At first I would get frustrated for starting but not finishing something, but the reality is that when I find the right piece, those moments you describe when walking past the keyboard and wanting to play happen frequently. With the wrong piece, they happen rarely if ever.
Good luck with the Gm prelude! It's one of my favourites which I have yet to attempt to play but hope to one day...