A month or so ago there was an entire issue of Scientific American MIND devoted to Stress, causes, effects and how to deal with it. The research suggests that by far the best strategy is to avoid getting into stressful situations, by good forward thinking, planning etc. Strategies for dealing with stress, such as modifying the way you think about the situation are only moderately useful (according to the research) in comparison.

I would say that it is reasonable to express a certain amount of dissatisfaction if other people have let you down. The approach suggested by Andy of dealing with other people's failures as if they are just another problem to solve might make you miss the most effective problem solving technique of all - a good kick up the ****!