I started writing a song a few weeks ago--don't worry, I won't pressure anyone into listening to it, ha ha.
I tried to do it with finger picking, but that's one of my weaknesses. I admit that I have to play it with a pick. It's not a difficult song to play, but some of the chords were not in my muscle memory. So I played those licks over and over until it feels natural now to go to those chords.
And while playing it over and over, I started exploring other chords and melodies so that the song is starting to develop.
My real point is: I love how muscle memory or whatever it is takes over and makes a song so easy to play. There's always a voice in the back of my head that tells me it's impossible, and each time, muscle memory works.
It's like a prize you get for practicing.