After discussions with Dr. Cobb, Frankie Faires, Aaron S and a bunch of other super smart people and tons of observation on my own, I am convinced that your movement quality (how well you move) is directly related to your mood!
Think of when you have an injury (like a messed up ankle in the past, um, not that I know anything about that from a certain snowboard incident) that makes it hard to move (or drive a car, or much else for that matter, so I've heard). How do you feel most of the time? I know from too much personal experience--not very well at all compared to normal.
How do you feel when you are really sick with a cold? Hung over for you crazy college kids? Like dog poo! How would you rate your movement at that point? For most, it is just above cat crap also---most walk around in a slumped posture and look like they are dragging a third leg.
Even beyond that, how do you know when Fido or Fee Fee the cat is ill (ok cats are moody bastards, bad example). You notice that they mope around and seem to lack energy---their movement sucks! Does Fido bark at you in morse code like a Lassie episode to tell you he is sick? If he does, call me up and we can make lots of money. You inferred how Fido feels from his less than stellar movement.
So, if your movement goes in the hopper when you are sick, what happens if do the reverse and improve your movement? Correct, you should FEEL better and your mood should improve! Sound insane?
Mobility training (like Z Health) is a great way to improve your movement and thus improve your mood! Does this work in every case? Of course not, but a vast majority of the time it works beautifully. I've seen it happen time and time and time again.
When an athlete comes to my place, my whole entire goal is to have them leave moving better than when they came in. I know to some hardcore strength trainers/coaches that seems insane and before your mind wonders too far I don't have them doing squats on a BOSU with pink foo foo weights either. Everyone works hard, but that does not automatically involve heavy weights and four letter words at EVERY session (although that happens too and loud music a great thing about the garage gym).
I know that if I can improve their movement, they will be one step closer to becoming a better athlete, gaining more muscle or vanquishing that muffin top. This may involve proprioceptive work (precise joint mobility drills like Z Health), eye/visual work, vestibular work (inner ear balance, so various head positions), kettlebell, tire flips, deadlifts, or even a lesson about why eating only 50 grams of protein a day is not the best. It all depends on what the athlete needs at that point.
It is a long term process and while there are some neurologic "tricks" you can employ for amazing changes in just seconds, the athlete still has to put in their reps with perfect form day in and day out and this include reps with the ole' fork and knife at the dinner table and counting sheep at night too.
I also know that if everyone leaves feeling like they got hit by a Peterbuilt and just as they got up just as the dump truck hit them too, at some point they are NOT going to want to come back day in and day out. If they know that it will suck to drive out and show up, but they know they will feel better once they leave--much more likely to make it each time.
The whole point is to ensure that your movement quality is ALWAYS good! You should get to the point that at the drop of a hat you can do virtually any exercise. Now, this does NOT mean to load up the bar to 400 lbs and start their for your first deadlift, it means to make sure you are moving well.
Moving well = feeling well along with increased performance. The best of both worlds.
Training should ENHANCE your life.