A major source of unhappiness, frustration and violence is the various intrinsic conflicts of interest. See Sex Differences and Social Conflict.

One cause of self-defeating behaviors is that the modern environment differs both from formative environments for human nature 10,000 to 100,000 years ago and the formative environments for western culture 200-5000 years ago. Both our innate and cultural behaviors evolved in an environment quite different from the modern one, so behaviors that served us well in the past may let us down now.

Many apparent paradoxes disappear when you accept that people are often unaware of what they are doing or why they are doing it.

How we understand ourselves has been heavily shaped both by common sense (or introspection) and by culturally evolved norms for productive social behavior. The first fails because we have conscious access to only a tiny part of what is going on, and this conscious access is filtered through a user illusion, and is driven primarily by the need to explain our intuitive understandings that arise from the interaction between our biases and our vast range of unconscious knowledge which we effortlessly weigh without any conscious considerations (see Unconscious and Representational Opacity). Our insight into our cultural norms is also flawed because they can (and did) arise without any accurate understanding of all their consequences (see Cultural Evolution), and also our socially approved stories must be understood in the context of individual/group conflict, where the needs of the individual are tacitly ignored, and public speech is under strong pressure toward worthy hypocrisy.