Not a mantra but works similarly: I recently bought a banjo, almost on a whim, to add to my repertoire for my YouTube channel. I got tired of of mooches complaining about my canned (royalty free) tunes.
I knew nothing about them other than the sound they make. The past week has BLOWN my mind.
Okay, back to the "mantra" part. The banjo strings are set up so an open strum plays a G chord. I watched a video from my banjo manufacterer, Deering, instructing on the clawhammer method. I find practicing this clawhammer technique extremely soothing, even if I goof. The instructor's best piece of advice "Learn slow, so you can play fast." That's probably why it is so comforting, 'cause I'm taking the time to feel the strings, hear the tones, etc.
That's my .02 cents for the day.