I have a timesheet and invoice tracker (http://www.getharvest.com/) which gives me a great overview into how much I'm working, how much of that is billable, how much is on my product or on research, how much is writing or networking events- and how much holiday I'm taking! I also report on the invoicing month-by-month which lets me see how the different balance of activities relates to income. I think I'm still learning which numbers are important, though.