President Bush has a (changing) standard for success in Iraq. But does he have a standard for failure? It's the kind of question I've faced with my clients in my work as an executive coach, helping leaders become more effective.

I met recently with a CEO client I've had for years. He has several pet projects that, in my opinion, should be shut down. His view is that, come hell or high water, they will continue until they succeed. We both have our perspectives, and many others have weighed in as well. At our recent meeting, I asked him to describe what success would look like. He did. But then I asked a tougher question: What is your standard that, if met, would leave no doubt of failure? Something that would say it's time to walk away from Business X or Project Y?

We discovered that he hadn't defined one. So as Business X limped along for nine months without scoring a win, and Project Y looked headed for defeat as well, there would continue to be plenty of opinions – but no definitive action. That's why we agreed on the need for a failure measurement that transcends opinions.

Great leaders set and stick with clear standards for failure as well as success. Others act like gambling addicts, greedily seeing only success, depleting their cash without any off switch.

Similar to my client's situation, there has never been agreement on the status of the war in Iraq because there are no agreed-upon measurements. Until such a yardstick exists, we can't agree about whether the US is winning or losing.

If we can't agree on present conditions, then it's critical that we have tripwires at both ends of the effectiveness spectrum: one for success, and one for failure.

The former is difficult to determine because it's shifted considerably. In 2005, the White House defined victory in Iraq in three stages that culminate in a peaceful, united, stable, and secure partner in the war on terror. But just this month, President Bush appeared to lower the bar, saying: "Either we'll succeed, or we won't succeed. And the definition of success as I described is sectarian violence down...."

Meanwhile, the tripwire for failure doesn't seem to exist.

Obviously, the United States must not share its failure guidelines with the enemy. But if such standards were crystal clear among America's leaders, we would see much greater consensus in Washington, if not an end to the US occupation of Iraq.

Gen. David Petraeus and Mr. Bush ask that we wait until we assess the "surge." They, like my CEO client, won't know when to give up unless they develop a failure standard.

Being stubborn helps leaders rise to the top. They like to get their way, to be right, and to win. Taken too far, that lovable bull-headedness becomes naked obsession, ego, or self-will – signs of addiction. Recovering addicts, like great leaders, know when to admit defeat. It's not too late for our leaders to set and stick with an objective, measurable standard for losing.

• David Peck is president of Leadership Unleashed, a coaching and consulting firm. He writes "The Recovering Leader" blog.