A while back, I read an article about how people who project confidence get ahead more than people who are quietly competent. I recently had the chance to experience that once again. It isn't exactly the same as extroversion vs introversion, but there is an element of that going on.
Similarly, in the past three years, I've been a part of several social circles focused around someone who is very good at making you think that you really matter to them, when in reality, they would throw you under the bus to get ahead. Just because someone is super-friendly doesn't mean they'll help you out. Lesson to take, IMO: it is entirely possible to like someone and not trust them.
Finally: some of the smartest, most interesting people are, at their core, fundamentally negative people. They can be (and often are) good, loyal friends. But spending too much time around negative people is likely to lead you to be more negative in the long run.
|Competence about to be taken down by confidence. Photo by Anne's pal Ned.|