Now take a look at marvin's situation. marvin said, "coach, i've been feeling tired and getting hungry and thirsty when i run lately. what can i do so that i have more energy? " what should the coach tell marvin?   "you should drink plenty of water while you run. we should also be sure you have a balanced diet and let you build up your exercise level."  "exercise improves your mental health by pumping you with endorphins. so you should drink more and run more and you'll feel better." "try eating power bars before you run and drinking caffeinated power drinks during your run. then you will have more energy and be less thirsty."