The first half of this episode of the Debug podcast is a fascinating insight into the job of a professional watchmaker. Jon Edwards' communicates with such passion on the subject.
I love the fact that in the watch world, any feature added to a watch is called a complication. Anything that adds extra functionality on top of telling the time, complicates the mechanism. This seems like a useful tool in the design of any product. It's another point of view you can use when deciding what features you need and how far you need to take them. Reflect on what you're about to design. As well as considering it as a useful and powerful new feature, also consider it as a complication, increasing complexity for both you and the user. As yourself - is this a necessary complication? If so, how can the compication be minimised.