If your people are always missing deadlines, it may actually be your fault. Research by professors Dan Ariely of MIT Sloan School of Management and Klaus Wertenbroch of Insead discovered that the way deadlines are set markedly affects performance. Using a complex proof-reading task, the academics gave Group A the usual single deadline - a straightforward 21 days ahead. Group B's task was divided into weekly deadlines. Group C also worked to interim deadlines, but were allowed to set these themselves.
Those given weekly deadlines averaged half a day late, while the single deadline bunch averaged 12 days. This condemns single deadlines to a deserved death but says little for self-management. Those left to their own deadlines came bang in-between.