Talking to Phil, Stephen, and PJ on FastForward Radio last night, I made a point that I make often in person but I don't think I've ever said on my blog.
The point is a reaction to accusations of doomsaying. People say, "you're so negative, contemplating catastrophic scenarios and apocalypse!" My response is that rather than being indicative of me being pessimistic or depressed, it is actually evidence that I am a happy person. Because I have a high happiness set point, I am enabled to consider negative scenarios without suffering personal depression or momentary sadness. I am immune from the reactive flinching away that most people have when they consider nuclear war or robots destroying all humans. Well, not entirely immune, but certainly more immune than most, and acclimation is part of it.
Because of my high happiness set point, there are greater volumes of idea space that I can comfortably navigate. Try it. Can you consider nuclear war in an entirely objective way, thinking about scientific facts and evidence, rather than fixating on the emotional human impact? For me and some of my friends, nuclear war can be brought up at a casual conversation, without gloominess, simply because it's interesting to work through the probabilities involved. We can be sad and humanistic/emotional about it too, but we have the option to be analytical as well. Others don't have a choice. More choices is good in this situation.
People with an average or low happiness set-point are unfortunately handicapped. They can't think about negative possibilities without feeling sad. Thus, that portion of the memetic state space is blocked off to them. Poor schmucks.
Ironically, their inability to rationally confront existential risks increases the probability that we will all experience a disaster. Unfortunate, because their actions will cause others to suffer.
A corollary of this effect is that when existential risks are brought up at all, it tends to be in a humorous context, because most people are too fragile to consider it in a non-humorous context.