I find that I go through productivity phases, generally the two I am most cognizant of are what I can loosely refer to as recharge and release.
When recharging I feel I read a lot more than usual. I catch up on a backlog of articles I flagged, dig into books I had been meaning to read, and generally find outside inspiration from various sources. I sleep and even eat more. The result is a focused sense of creativity and determination in my own work. I get the urge to update my website, portfolio, and blog. I dust off personal projects that had slipped away from me and give them another chance. I sleep and eat less and typically can focus on tasks longer. Leading inevitably back to the beginning.
I suppose that makes sense, it's pretty easy to burn oneself out by working too much and a person can only read and rest so much before the urge to create flares up again.