There's a soundbite I like to use in an agile context: if it hurts do it more often. Its surface illogicality makes it memorable, and there's a real truth in there. Many difficult activities can be made much more straightforward by doing them more frequently. XPers are particularly well known for applying this principle to testing, integration, design, and planning...
In my early years as a developer, I was privileged to work on a project managed by Sharon Weinberg, now president of the Codd and Date Consulting Group. She was a walking example of much of what I now think of as enlightened management. One snowy day, I dragged myself out of a sickbed to pull together our shaky system for a user demo. Sharon came in and found me propped up at the console. She disappeared and came back a few minutes later with a container of soup. After she'd poured it into me and buoyed up my spirits, I asked her how she found time for such things with all the management work she had to do. She gave me her patented grin and said, "Tom, this is management."
Sharon knew what all good instinctive managers know: The manager's function is not to make people work, but to make it possible for people to work.
Peopleware, pg. 34, This Is Management
Projects on which the boss applied no schedule pressure whatsoever ("Just wake me up when you're done.") had the highest productivity of all. Of course, none of this proves that Parkinson's Law doesn't apply to development workers. But doesn't it make you wonder?
The decision to apply schedule pressure to a project needs to be made in much the same way you decide whether or not to punish your child: If your timing is impeccable so the justification is easily apparent, then it can help. If you do it all the time, it's just a sign that you've got troubles of your own.
Peopleware, pg. 29, Some Data from the University of New South Wales