Keep in mind that natural selection does not select for traits, it selects against them. The first question you need to ask is not, "is there some advantage?" but rather, "what are the disadvantages?" Not all traits exist because they are advantageous; many may persist because they are not particularly disadvantageous.

The second thing to keep in mind is that many traits form a spectrum (particularly psychological traits). While the endpoints of the spectrum will likely be very problematic, there may one or more areas in the middle of the spectrum which are advantageous. Furthermore, it may be advantageous to have a variety of the trait in a population.