There are two types of situation where I think that the old KISS maxim (Keep It Simple Stupid) is worth remembering.
The first is involves any course of action (e.g. making, doing, going). Keeping it simple will help get you started, and in all sorts of ways thereafter.
The second relates to explanations (e.g. reasons, causes, diagnoses); the law of parsimony says that the simplest is the most likely.