Abstract
The quest for happiness has expanded from a focus on relieving suffering to also considering how to promote happiness. However, both approaches have yet to be conducted in an evolutionary framework based on the situations that shaped the capacities for happiness and sadness. Because of this, the emphasis has almost all been on the disadvantages of negative states and the benefits of positive states, to the nearly total neglect of 'diagonal psychology', which also considers the dangers of unwarranted positive states and the benefits of negative emotions in certain situations. The situations that arise in goal pursuit contain adaptive challenges that have shaped domain-general positive and negative emotions that were partially differentiated by natural selection to cope with the more specific situations that arise in the pursuit of different kinds of goals. In cultures where large social groups give rise to specialized and competitive social roles, depression may be common because regulation systems are pushed far beyond the bounds for which they were designed. Research on the evolutionary origins of the capacities for positive and negative emotions is urgently needed to provide a foundation for sensible decisions about the use of new mood-manipulating technologies.