Bosses matter. They matter because more than 95 percent of all people in the workforce have bosses, are bosses, or both. They matter because they set the tone for their followers and organizations. And they matter because many studies show that for more than 75 percent of employees, dealing with their immediate boss is the most stressful part of the job. Lousy bosses can kill you—literally. A 2009 Swedish study tracking 3,122 men for ten years found that those with bad bosses suffered 20 to 40 percent more heart attacks than those with good bosses.

Bosses matter to everyone they oversee, but they matter most to those just beneath them in the pecking order: the people they guide at close range, who constantly tangle with the boss’s virtues, foibles, and quirks. Whether you are the CEO of a Fortune 500 company or the head chef at a restaurant, your success depends on staying in tune with the people you interact with most frequently and intensely.