Don't forget sleep! Big influence on mood which affects your listening enjoyment. I unsure about actual hearing though. Thanks for the encouragement to get more cardio, maybe that will help my ringing.
Seriously though, maybe the best tweak is exercise?
I posted, mostly in jest, before that cleaning your gear would yield fantastic sounding results. Yes, it was a joke, brought about by the fact that I thought the sound was better afterwards. Of course it was probably placebo ... but what if the actual cause is moderate exercise?
So, audiogoners, I challenge all of you to go out, put some bug spray on, and put your fancy iPhone or Android HR monitor to good use. Then sit yourself and your sports drink down and listen.
Does it sound better?