Procrastination is a symptom of something happening in your brain. You do it for a reason. However, everyone has a different reason.
For example, I have a friend who procrastinates with every major report or project. She is afraid of making a bad grade, or so she says. In reality, she puts off the project because if she starts it too soon, she will loose the will to do yet. Even if she adores the project's goal, she will put it off so she will love it while she does it. Though if she started maybe a week sooner, she would make a letter grade higher. She always makes a B with this method when everyone knows she can make a perfect A, but runs out of time. Part of it has to do with her having ADD.