I find weighing myself once a day in the mornings helps to keep me on track, and sane. If I see a lower number I may use some of my weekly points and have a glass of wine with dinner, or a peanut butter cup for dessert. But if I'm a little high, it keeps me within my daily points, and I up my activity points.
I try never to obsess about the little shifts, it's all about the big picture!