Why has natural selection has left us all with fragile minds? Drawing on stories from his own clinical practice, Randolph Nesse shows how negative emotions are useful in certain situations, yet can become overwhelming. Anxiety protects us from harm in the face of danger, but false alarms are inevitable. Addiction and anorexia result from the mismatch between modern environment and our ancient human past, and there are good evolutionary reasons for sexual disorders and for why genes for schizophrenia persist. Taken together, Nesse's insights help to explain the pervasiveness of human suffering, and show us new paths for relieving it by understanding individuals in a broader context.