I LOVE the grinning technique! That is brilliant. Grinning actually releases neurochemicals in your brain that are associated with pleasure. So that is definitely a win-win.

id also suggest, when you’re working on some music and you notice there is a part where you tend to tense up, isolate that part and practice it by itself slowly, WITH incorporating a a calm slow breath as you play the riff.

it feels a bit like adding another ball to the juggling act, but a slow deep breath while you are playing counteracts the body’s inclination to tense up. The tensing up will certainly restrict the musical flow of the hard parts. See if you can consciously incorporate a breath into th process to let your body experience the fact of playing the riff while in a more relaxed physical state.

hope this helps - Lisa