One concept in Psychology that I think I'll remember 5 years from now is the development of the mind. This is because I've already spent so much time outside of class applying the ideas of nature v nurture, attachment styles, class/race differences, etc. in the context of others' behavior. This class has provided me with an interesting lens through which to observe how others behave. If somebody is acting in a manner that I am totally baffled by, it's fun to try and look at the world through their eyes and empathize. Basically this class has taught me that there's a somewhat "logical" reason for everything that everyone does. Something that somebody else does that may seem stupid, or irrational, or downright crazy to me would usually seem like a rational thing to that person.
A second concept that I'm going to remember is Kohlbergs theory of morality. The entire morality unit has made it so that I strive to achieve post-conventional morality for important decisions, and not just stop at conventional. This is hard, but I believe that this idea will help me make better decisions throughout my life.