Diagnosing emotion disturbances should be informed by current knowledge about normal emotion processes. I identify four major functions of emotion as well as sources for potential dysfunctions and suggest that emotions should only be diagnosed as pathological when they are clearly dysfunctional, which requires considering eliciting events, realistic person-specific appraisal patterns, and adaptive responses or action tendencies. Evidence from actuarial research on the reported length of naturally occurring emotion episodes (including potential determinants) illustrates appropriateness criteria for the clinical evaluation of emotion duration—an essential element in the DSM-5 symptom catalogue for major depression episodes, especially in bereavement. The need for more actuarial evidence on normal emotion responses and its consideration by the clinical community is highlighted.