Drawing on scholarly treatises and on physicians’ consilia and case histories, this paper first looks at the early modern physiology of affects. It underscores the high degree to which the affects were seen as somatic, physical phenomena rather than being attributed only to the mind or soul. Their primary site was the heart, in a very concrete, not just metaphorical sense: they were understood as movements of the heart, the spirits, and the blood, away from the heart toward “attractive” objects, for example, in joy, and back to the heart in the face of negative, repulsive objects, as in wrath or fear. In this sense, the term “emotion” was used, in the seventeenth century already, to refer to the movement of spirits and blood that resulted from strong affects. As somatic phenomena, strong negative affects, in particular, like anger and grief were widely perceived as powerful causes of all kinds of diseases. Drawing on hundreds of early modern letters penned by laypersons and approximately seventy early modern autobiographies, the paper then looks at the lay experience of affects. Laypersons also perceived the affects largely as somatic phenomena and attributed many illnesses to them. However, they seem to have believed to a very limited degree only, that the affects or passions could be controlled, as the physicians recommended for health reasons. They sometimes even attributed diseases to the fact that they had restrained a strong affect rather than venting it—just like they considered “obstructed” excretions a major cause of illness.