Since I haven't used a power meter in a number of years, and I work out on a dumb (not a Smart) trainer, I've had to rely on the knowledge of the gearing that I use on the trainer that I've used for years and years. It may be an iffy assumption, but I assume that using the same gearing combinations on the same trainer will give me the same resistance year over year. I have a cadence sensor so that is a known part of the equation as well. Throwing out the window the wear on the trainer, I've gone with this for years.
Things went wrong this year when I started my detailed workouts on the trainer. I'm using a different bike this year than last, and the gearing is different. Actually, every year over the last 10 I've used different bikes and I've done the math. Never mind, I thought, I'll compensate a bit this way and a bit that way and call it good.
That would have worked. Actually, it did work. But I've been suffering like a 300-pound cyclist in the Pyrenees. That's because.... I didn't do the math. When I actually counted the teeth on the cogs I was using, I concluded that I have been doing my hardest workouts to START with. The bright side is that I have still been killing the workouts (and perhaps it's slowly killing me, too).
The bad news is that I am still capable of the biggest rookie mistakes.