I think one of the best parts of being in the middle of my first real race training season, is that I keep running my longest distance ever. 14, 18 and now 21 mile distances are the longest I've run, the last was just this Sat. My run Sat was great. I was a bit creaky for the rest of the day, but spent some time rolling out my legs with a rolling pin and staying hydrated and I felt fine.
I keep coming back to mental tools in these posts but they are really important in longer runs. When you're getting worn out you start to lose focus, get a little slow mentally and that's not the time to relay on your creativity to get you through low spots. That's the time to rely on your preparation and strategies you have worked out in advance...and caffeine.
I use a few "tech" foods to get through runs that are longer than 12 miles. Anything under that and I don't even bring water along, but at 12+ I carry a water bottle and start with the Gu shots and salt pills. I had never tried electrolyte pills, but used them on my 3hr trail run last week and was amazed how much they helped. I just felt better in general during the run, less run down more on top of things mentally. I had been running with an electrolyte solution mixed into my water bottle, but it was sweet, I got sick of the flavor and I don't think it worked as well. I took the pills 3 times an hour and at the end of my 21 miles I was peeing nice and clear within an hour of finishing, hydration achieved.
The other thing I used was Gu shots. For those of you who aren't familiar they are packets of sugary syrup that you take a couple times an hour to keep glucose in your system. In order for your body to burn fat, which is what you want to do on a long run, it needs glucose to burn as well. Fat is the source of energy for long duration exercise. Back in school we used to say that fat burns in a glucose flame. Without a dietary source of glucose your body will attempt to provide it from internal stores which leads to destructive catabolism, bad news.You need to take in something to burn to keep you moving and it's only the ultra running folks who are stopping for pizza and burgers mid-100 mile run.
The last hour of my longest two runs I've had Gu chews with a touch of caffeine. It was just the kick in the pants I needed. In the last legs of a long run my legs start to feel a bit fragile and while I never really get demoralized or exhausted, a little rush from the caffeine really makes things flow nicely at that point. Rather than drifting in and out of focus it puts my head back in the game. I'm definitely a pragmatist when it comes to this. I've also done longer runs where I ate mostly corn meal, or stopped by the house often enough to grab peanut butter on toast regularly. These worked fine and my stomach handled it well, but the tech stuff just fits in a tiny pocket in the back of my shorts and I can just stop at the house every hour to refill my water and get a smile from the fam.
A long run is not something you just stumble out the door for. Taping nipples, lubing thighs and taking stock of gear will keep you from a world of pain later. I've had rug burns on the insides of my thighs for days because I wasn't paying attention during a run...and chaffed nipples?! Worst shower ever!