Very careful time tracking is valuable on many levels.
Recently I shifted from "how is the quality of how I'm spending my time?" style tracking (EX: categorize into "excellent", "good", etc) into "what activities am I spending my time on?"
It's always amazing and surprising to see how little time working is required to do a task, but often the time spent "at work" is much higher than that.
For instance, I finished an absolute beast of a bear of a task in 7.2 hours (425 minutes) of full-on work across two days. It seemed like the kind of thing that would take a long time, but it was only one full day of working.
But I notice if I'm not careful, I'll spend maybe 2-3 hours in a day doing the most important types of working and then spend a lot of time "at work" -- sometimes doing very valuable things, but by definition, almost never as valuable as the most valuable thing.