Often things aren't just good or bad. Here are five examples: (1) solutions for problems can create new, often unexpected, problems, (2) good traits of a person can arouse envy in others, (3) what can be a strength in one situation can be a weakness in another, (4) the fact that you have achieved success feels good but can decrease your motivation to make further progress, and (5) having much knowledge about a topic can be pleasant but can create some difficulties in the communication with others. I want to say a few things about this last example which is related to a phenomenon known as the curse of knowledge (Loewenstein & Weber, 1989).