I've always been a lone wolf. In college, lots of the guys on the team needed to run with someone else, or they would lose motivation and the quality of their workout would suffer.
My training philosophy in high school was derived from two quotes. One from Percy Cerutty: "While a man is racing, he must hate himself and his competitors," and the other from Tom Fleming: "Somewhere, someone in the world is training when you are not. When you race him, he will win."
In College, the talent pool was a little different, so I modified Fleming's quote to, "Somewhere, someone is training smarter than you. When you race him, he will win." I could never run more than 90 miles a week without burnout, but running in a group, I was pressured to do so. Now, a couple years later, I am training at a higher level, lone wolf-style again.