Sometimes, you get tired and want to quit midway. This has happened to me on more than one occasion. I've asked myself the same question multiple times. The question is, "Why am I doing this?" When we ask ourselves this question right now, we may be able to answer it, but when we're in the middle of a long run, a big report... something major, we're mentally exhausted and we don't want to continue.
At those times, you need to push on through, because if you stop, all that moment you've built up thus far will dissipate... and you'll have to build it up again. There are times when you take breaks, but there are other times where you need to keep truckin' on. In a mile, the truckin' time is between a half mile and a three quarters mile. That's when you've finished half, but still have another half to go. In order to get past negative thoughts like that, you need to attack it with positive thinking, pushing yourself to go on. Putting that into your head is important because without it going in your head, you become weaker and weaker until you actually do stop.
When tough times come, you have two choices, to keep going, or to stop. Choose to keep going and you're gambling whether or not you'll make it because you're pushing hard, but if you stop, you definitely won't make it.
Keep on truckin' and move forward.
(as for today, I only did 15.85 miles in 1:01:30)