I'm not trying to be flippant with this comment, but I once overheard a high time instructor telling his student at a debriefing that..
"what you need to do is un-clench your arsehole and stop trying to chew a hole in the seat cushion".
The student took this to heart and reported the next flight as a revelation!
PS, I'm an AME so it may not work and the standard disclaimers all apply.
