I remember being 27 and John Colosimo and I were sitting around talking about the same thing. I really clearly remember it. So, 21 years later...I "sorta" laugh about it. One thing that was hurting me at the time was that "gear change" of life.
You know, we both stopped simply doing fun stuff...like just tossing the frisbee between classes and chasing around and playing tag and all the other stuff. More sitting, less playing.
One thing that helped me a lot was to insist on more wandering around. At my old job, I got up every fifty minutes and did something for ten. By the way, no one ever noticed it. Ever. I would drop in other offices, make coffee, look busy, but for ten minutes, I walked around.
It's not a perfect answer...but I am convinced that you just need to add back a lot of that low level stuff like walking and moving around. Next, when you do train, try to always add something new and fun...the worst thing you can do is get on a row of machines and act like an 1890's factory worker. I have more to say on this...