Challenge Accepted

I accepted a challenge today from a girl I work with. She has been attempting to lose weight for alittle longer then I have and so far she has lost 22 lbs. I was explaining to her how I'm going about losing weight and she was explaining to me what she was doing. Out of the blue she popped the question.....how about a weight loss challenge? At first I wasn't sure because I'm trying to take a more laid back approach to my weight loss this time and not put so much pressure on myself to be perfect. She told me to just think about it and let her know. Well I thought about and decided why not? We agreed there should be a prize at the end but we weren't sure what. I suggested a gift card of the winners choosing but what amount?....we both agreed on $25.00. The only terms to our challenge is that it runs from November 1st to January 1st and the person who loses the most weight wins. Luckily we are only 9 lbs different in weight so we don't have to worry about figuring percentages or anything like that.....just plain and simple.....pounds lost. I'm so excited about having this new motivation to keep me going and trying harder. So what do you think?.....do challenges motivate you more or stress you out to the point of giving up? Should we weigh in each week or wait until the end and weigh in? I see benefits from both ways .....not knowing how much she has lost will push me to work harder and eat better, but knowing she has lost more could make me give up. We have decided to wait until the end.....so I guess we will find out in two months. Let the challenge begin!