I am a real data geek and have about 2,000 lines in a spreadsheet of all the time I have booked to clients in 2017, combined with the number of words I wrote, the type of article, and how much I was paid. At some point, I plan to go through there to see where my best return on time invested is. I can then use that to get rid of the lower value work and revise my rates so I am making consistent money in all topics.