In the world of business (especially big business), you hinge many decisions on critical assumptions - but what do you do when, let's say three years later, those assumptions are proven wrong?
Well, you do the most logical thing you can do (which is probably the hardest thing to do) - you own up to it. You admit the assumptions you based your decisions on have been proven wrong. You take your lumps and get on with your day. We can not be 100% right in our planning - in fact if we look at the world of venture capital - they basically expect only 2 or 3 successes out of ten. That means, they put money in 10 deals (sometimes multiple rounds) and only expect 2 or 3 to succeed.
But many times, our top business leaders continue to allow their egos to get in the way. The past few years we have witnessed many colossal failures - think Enron, Worldcom, Bear Sterns - I bet in each one of those cases there was a point to which a decision was made to "go full steam ahead and damn the torpedoes". Now, admittedly, if they would have come out the other side, these companies would be hailed as "titans of industry" again (cause they were darlings before).
The point is -- there is point where admitting you made a mistake is the most prudent course of action. But there is also a point of no-return if you don't. So, as we look into the abyss of the current economic situation - be willing to admit mistakes, be willing to ask for help, and don't view either of those things as a sign of weakness - either personally or professionally.