This morning, when I started my 3 miler, there was a middle aged man who was running about two tenths of a mile ahead of me, and I judged him to be slightly slower than me, so I made it my goal to pass him. This was a little harder than I had orignally assessed. Either he was faster than he looked, or I was slower than I assumed, because I spent the first half a mile chasing him down.
Then, when I finally did pass him, he was close enough behind me that I couldn't slow up, so he actually provided me with the necessary motivation and momentum to finish my first mile in 10:20. The speed (yes, it's all relative, and right now that kind of pace counts as speedy for me) carried through in the remaining two miles, and I finished the 3 in 31:14, which I do believe is the fastest 3 miler I've had since returning to running.
And this is why I miss racing: Having other people in my sights to slowly pick off and pass provides just the right amount of motivation to push myself past my comfort zone. Granted, my targets are often the elderly and small children, but still, the satisfaction of passing a ten year old is priceless for the ego. And those old people can be surprisingly fast, so sometimes overcoming them can be a feat in and of itself.