I love the timed challenges (and really need to participate in more of them). They make you get off your butt and work on them without sweating the details. You are more interested in making something than making sure it's "nice." And this helps to reinforce that you CAN create something. I missed this year's 24-hour comic day because I didn't know it was happening until a couple days before and I had other things to do, but I did participate in Dragon*Con's Comic Quick Sketch Contest, where you have an hour to come up with either a sequential page or a finished illustration. And it wasn't all that bad.