For context about 30 day challenges, watch this Ted Talk by Matt Cutts.
I'm trying an experiment for the month of August - not watching any television or movies. I've never been someone who watches a ton of TV, but when I get into a show I can power through a ten episode season in a week. Throughout July, I spent more time in front of the TV than usual, and some of my other activities have fallen by the wayside as a result. I got to a point where I was in the middle of four books simultaneously, and working on three concurrent programming related side projects. When you add that to everything else I have going on (Ultimate frisbee, Taekwondo, preparing talks for conferences, seeing friends, walking my dog, push-ups, work) it became unsustainable. I would get a little overwhelmed by my schedule, and default to mindless activities to relax.