I play/practice the piano for some decades and when improvising (Jazz, Romantic, and sometimes even Baroque), I observe a certain magnetism of the C Major key. I'm able to play scales, arpeggios, ...
I've been playing guitar for some time, and often when i do improvisation exercises, I hit notes which sound too tense to finish a run/lick/riff on. Kind of like having a sentence which no full stop. ...