Ten-mile runs are my favorite, except when they're very much not. On a good day, I finish the last mile exhausted but relaxed, segue right into a stretching and rehydrating session, shower, and chill the rest of the day feeling great. On a bad day, I'm stiffening up at mile three, staring down the endless road ahead of me with dawning horror as I realize that every one of those 10 miles is going to be leg-cramping, lung-burning, head-pounding torture. Running: it's really hit or miss sometimes.
Sometimes the only reason I run is for the feeling of being done with a run, and that holds whether it was the most amazing, transcendent, meditative, figured-out-the-meaning-of-life run or the one where I get crabby with kids riding bikes on the path because their smiles are too happy. The run is always worth it; sometimes, it's just a matter of getting it over with so I can make it to that part.
After 11ish years of running, I have a decent set of tricks to get through the tough stretches of a long run and make it to the end alive. Note that if you are seriously hurting during a run, whether it's pain in a muscle or difficulty breathing, you should stop running, take stock of what's going on, and end the run early if you need to. No single run is worth pushing past your limits to the point of injury! But if you're feeling tired or unmotivated, or are just desperately trying to find ways to get through runs that feels endless, here's what keeps me going; maybe it'll help you too.