All things mentioned can and do effect your playing. Not to mention moving equipment if your playing a gig. I guess the only weapons we have to fight it are, stay iin shape with exercise or Yoga, Eat right for energy, keep you mind active with different activities. I still like learning new songs even though I'm not playing out much anymore. I think just going to my piano and playing for a short time each day helps keep the chops up. Even if its just running thru scales and arpeggios. Just playing the arrangeer makes you lazy. For memory I just use my iPad for my music and I've gotten back into reading more, even taking notes as I read a book, its remembering that persons name you just met thats gets me LOL!
Just keep on keepin on