*If you do keep a detailed log of your workouts, what kind of actionable data do...

If you do keep a detailed log of your workouts, what kind of actionable data does that information provide you? Do you refer back to it daily, weekly, monthly and try to optimize your workouts based on your previous history? If so, how?

I used it to run experiments for my self quantification project. I even have an work-in-progress essay about it too: http://kibabase.com/articles/self-quantification

Granted, I can't do much with a sampling of only 1 person, and I only finished one experiment after collecting 30 days worth.