Once upon a time people firmly believed that thinking and feeling were two separate capacities, destined to often clash. As 17th-century Dutch philosopher Baruch de Spinoza put it, “When a man is prey to his emotions, he is not his own master, but lies at the mercy of fortune.” By this logic, the intensity of experiences such as sadness, anger or fear can trump our reasoning. Yet modern research tells us otherwise. We are not slaves to our passing passions; rather we regulate emotions all of the time. You resist exploding at a client just because he is tardy, and you manage not to throw things at the house next door during their noisy barbecue. Controlling anger and frustration keeps our professional and private lives on track—and prevents irksome situations from escalating.