I know of that feeling, and I loveit/thriveonit too. Comes with insane and dangerous speed combined with extreme physical exertion... I haven't felt it to a superhigh degree in a long time. The last time was probably more than one winter ago, while racing downhill at breakneck speed on my snowboard. I haven't had a good snowboard trip since college. If I had a road bike right now, I'd go riding with you to see what it's all about. Or maybe we can go get ourselves on runners' high one of these days. Gimme a call...