Want to be one of the greatest leaders of all time, with a wealth of success, power and respect? Try doing nothing for a change, says Harvard historian Nancy Koehn. This counterintuitive advice applies to moments of crisis, when the stakes are high and emotions are tense, because that is the very time when you’re apt to make errors in your decision-making. Anger brings weakness, but you can conquer the trap of emotion by removing yourself from the situation, and sitting in silence to think. To prove that doing nothing in times of severe anger is a leadership skill worth developing, Koehn tells the story of the most important letter Abraham Lincoln never sent—if he had had email or twitter (i.e. quick reactions) back in 1863, the outcome of the Civil War and U.S. history may have been drastically different. It turns out you can win almost any fight if you learn how to respond thoughtfully in time, instead of reacting rashly in an instant. Nancy Koehn is the author of Forged in Crisis: The Power of Courageous Leadership in Turbulent Times .

Nancy Koehn: One of the most interesting and powerful lessons that I discovered in writing this book was that each of these five people — that’s Ernest Shackleton the Antarctic explorer; our sixteenth president Abraham Lincoln; the abolitionist and civil liberties crusader Frederick Douglass; the resistor to Nazi Germany’s evils Dietrich Bonhoeffer, a pastor; and the environmental activist Rachel Carson, discover that sometimes doing nothing is the most powerful, the most significant, the most influential thing a leader can do.

And they discover that mostly by making mistakes, by acting quickly, decisively, rashly in a high stakes moment when they are highly charged, when they are emotionally very hot in terms of their temperature, and when people around them are emotionally very hot in terms of their emotional temperatures. They discover the power of waiting, of doing nothing when the stakes are high and emotional temperatures are high. And they discover this lesson because they make the mistake of acting, of writing, of speaking out, of making a decision when they are very, very hot under the collar, right? When their hair on the back of their neck is really on end. And they realize, “This is not my best mode. This is not my strongest self. I can actually do a lot of damage to my mission, my followers, what I’m trying to accomplish if I make choices when I don’t see myself as clearly, when I’m not as temperate and careful and thoughtful and reflective and emotionally aware as I might be.”

And so one of the best examples of this is an example that occurred right after the Battle of Gettysburg. And I tell it in the conclusion to the book. Abraham Lincoln has just learned that the Union Army, commanded by a general named George Meade, has won a decisive battle in three days of bloody fighting in southern Pennsylvania in Gettysburg against Robert E. Lee’s Army of Northern Virginia. Lee immediately, after the third day and the defeat, retreats south for Virginia. And George Meade makes a critical decision at that moment not to pursue Lee’s army even though Lee’s army is weakened, suffering from great casualties and emotionally demoralized. But George Meade makes a decision, he thinks it’s very well-founded: his troops were too tired. He can’t risk really taking any more losses than his big army, the Army of the Potomac, has already taken. Losses on both sides at the Battle of Gettysburg were enormous. Lincoln learns of this a day and a half later by telegraph in the White House and he is so frustrated, so angry, so beside himself—he’s pacing the halls of the second floor of the White House in anger and frustration, and he writes a four-page letter to George Meade expressing his dissatisfaction. The dissatisfaction then gives way to anger, the anger gives way to red-hot frustration on the pages as Lincoln’s pen gathers speed and his emotional temper gathers speed. And he writes this letter, “You know, you have no idea how disappointed I am. You could have pursued Lee, crushed that army and ended the war, and now countless deaths are still to come and the end of the war is nowhere in sight. I cannot express adequately my disappointment in this situation.” He writes this letter. He folds it up. He puts it in an envelope, and it’s found after he died. “To George Meade,” says the signature on the front. Written but never signed or sent, July 1863.

And when I teach this letter to my executives, when I do leadership coaching or when I present it to my students I say: Imagine if Lincoln had had email, because what Lincoln did in that moment — I can see him doing it; I've spent a lot of time with Mr. Lincoln over the years — I can see him sitting back or maybe getting up from his writing desk and taking a long perambulating walk around his big office and saying, “Wait a minute. I don’t really have very many generals that I can call fighting generals in reserve. If I make George Meade angry and he peels off the Union war effort I’ve already gone through a lot of generals that have disappointed me, and lots of them aren’t my friends.” So I think he made a very calculated decision, that as frustrated as he was and as disappointed as he was, he was going to sabotage or do some damage to his mission, to save the Union and end slavery, if he alienated George Meade who would ultimately talk about it and alienate other generals for Lincoln.

And so he never sent that letter, and I always say to executives: imagine Lincoln had just hit send in the heat of the moment if he had email. Or sent a Twitter message off excoriating Meade. The course of world history, certainly of U.S. history, might indeed have been different. So Lincoln gained a great deal by not sending that letter. The Union was preserved. Great fighting generals came out of the West by early 1864, Sherman and Grant, to fight the war that Lincoln knew that needed to be prosecuted. And the story turned out, in the end, a triumph for Lincoln’s mission. But he had to exercise the discipline. He had to realize that doing nothing was the best thing he could do. And we have to learn that lesson today. We live in an age when world leaders are expressing vitriol and hatred and their immediate reactive white-hot emotions in all kinds of media channels because they’re not waiting, they’re not processing, they’re not taking a yoga breath and they’re not considering that those emotional expulsions are doing more damage to the world and their followers and a noble cause than simply remaining quiet and doing nothing in the heat of the moment.