Seth Godin recently wrote a great blog post Investing in Slack.
Most of my mistakes as an experienced architect have been due to a lack of slack.
Corners get cut when moving fast on that adrenaline rush of a looming deadline.
When corners are cut, regrettable mistakes happen.
Unforeseeable errors are an unpleasant fact of the profession, but regrettable mistakes gnaw at your soul. Just give us a couple more hours!
The hard part is managing a project is getting the slack before we need it.