So I down the fluids. If you drink at least eight glasses of water a day, there's nothing you can't do. I keep a gallon jug of spring water in my mail truck, and I order my streets to make sure I come back by the truck every so often. My daily goal is to drink the whole gallon during the 8 hours I'm carrying the mail. It's fuel, really.
Breakfast is a biggie.
I find that my energy level stays about even if I keep an even pace throughout my route. When I'm carrying lots of mail, I usually have my arms up in the air a little bit, but when I'm carrying less, I try to pump my arms vigorously. I find it helps with my momentum and my breathing, which tends to be more rhythmic and regular when I use my arms as well as my legs. I swear by the extra layer of protection and cushioning. I use the same strategy when I run trails or mountain-bike after work, too, because the double layer seems to protect my feet better than any type of shoe insert or padding.