Most people who have sat through any basic algebra class are familiar with the concept of the slopes of lines. Slopes, or the measuring of a horizontal change of a line against the vertical change, can make for excellent metaphors. I, for one, like to think of the probability of me achieving my goals over the course of the year as one immense, negative slope. The horizontal change of the line represents the amount of time that passes. The vertical change represents my productivity levels. In short, as time goes on, I...