Why should anyone spend the time and effort needed to compile a short-term financial plan?

A short-term financial plan generally projects cash flows at least one year into the future. Oftentimes, the actual cash flows vary significantly from the original forecasts. Why then, should anyone spend the time and effort needed to compile a short-term financial plan? 

Most people need a goal to work toward in order to succeed. Even though it may vary significantly, it gives you a figure to strive for, and hopefully exceed. Then when you do exceed it, it’s a great feeling that you wouldn’t have if you hadn’t set the original goal.