general body conditioning does wanders (i.e. exercise more), higher metabolism rate helps your recover better, build muscles in the right places, be better alert. I used to do endurance riding and in the periods of too much work (office job), anything physical would tax me quickly.
I'd avoid too much stimulants. Coffee brings you up, but when it leaves the body, it does so fairly quick and some people have hard time noticing the change. So on long trips, I never drink coffee.
Another long distance riding trick is to use a few lemon sour drops, the really sour ones. Those really jog your senses for a little longer.
Another trick is a whiff of ammonia smelling salt, the ones that are used to bring some one out of fainting. Same thing, senses kick in fast.
Also, taking a 5 min brake and do a few jumping jacks.
I think that the most difficult parts in training, like that last rep while lifting, is what give you the most benefit. You got to make sure that you are not trying to just empty the clip and making each shot count.
My old shooting instructor had a reverse solution, if you were shooting badly, he would give you 5 shots to do in 30 min
it sucked, it was embarrassing, but I'll tell you, I'd not take a shot just to get it out.
, ok may be that's too crazy.