Not a designer. But yes.
Maintain three daily logs:
- Full time job
- Side project
- Personal chores
Log in 3-4 deliverables / things to complete in a day against each.
Do a weekend review on where & how much I fell short.
I track my daily focus and productivity by tasks finished, more importantly, the tasks that I've set myself finished.
So task based measurements of productivity.
If you're designing an app for tracking productivity, I think something more completion based rather than time based would work relatively well.