I was going to push this until around midnight, but I since I already feel like going to bed...
I'm not going to make excuses (WORK! IT WAS WORK! Also, it took me all day yesterday to write one scene. Do you know how difficult it is to have your characters flirt while writing a geometric proof?), but obviously, and not surprisingly, I did not even come close to my 20 page goal. The final count: 7 1/2 pages. So not even half.
Which isn't to say that all the effort got me nowhere. I finished two chapter revisions and I have 28 out of the 50 pages I need for the contest entry. I feel good about where these revisions are going and the consistency in the voice. I feel more motivation now than when I was about halfway through the book.
I guess the moral of the story is that it's good to challenge yourself. But also, don't hold yourself to too high of a standard. It's ok once in a while to set a goal that you know you won't reach, just because you'll work so hard and end up getting a lot done in the process. But doing this over and over again can lead to a lot of disappointment, and you may lose your motivation altogether.
So, yes, challenge yourself. But don't be ridiculous.