Since 1992, I've counted about twenty tourists who died because of their overoptimism. P is for paranoia, an undesirable quality which seems to evolve naturally from carrying around too many worries while travelling. See N above and X below. Q is for Quixotic, an adjective well applied to people who stir up shit for no good reason. I never do that, of course.
R is for respect and for rip-offs.
If you can't show respect, you shouldn't travel. On the other hand, if you behave respectfully all the time there are lots of people in the world waiting to take advantage of you. Balancing these two things seems to be a skill which takes endless refining. S is for simplicity, the key to success while travelling. If you don't have many plans they can't go too far wrong.