What happens when we move back deadlines? Research suggests we have a lot of difficulty using our newly-found time wisely. We wind up facing the same problem again -- only now we've gone an additional week, or month, or year without reaching an important goal.
Human beings are generally pretty lousy when it comes to estimating the time they will need to complete a task. Psychologists refer to this as the "planning fallacy," and it's an all too common problem.