I know if I'm going fast enough or slow enough for races if I'm passing everyone else I see.

So, as it turns out, I know I'm going slow enough.

Over in the Road subforum, they sometimes talk about training with power meters. This would work in a situation like I described yesterday, which was riding loops in 20+ mph winds. My speed varied by nearly ten mph even with the same perceived effort thanks to whether I had the wind at my back or in my face. Keeping track of effort with a power meter would have been more useful and consistent, and likely less depressing, too -- 300 watts is 300 watts regardless of wind direction and road speed.

I treated that ride like I play golf -- I don't care about the score.