The basic principle is the same: If your explanations, constructs, or theories get real complicated, they are probably wrong. This is especially likely if you have to keep making special case elaborations, where each new piece of information requires modifications that make things still more complicated.
I'm increasingly of the opinion that "K.I.S.S" applies to relationships with self and with others. When we're constructing ever more elaborate explanations for behavior or feelings, we're usually missing a key simplifying concept.
Sometimes we are downright willfully ignoring it. A classic is when an important relationship is obviously toast, but we don't want to see that. I can continue explaining away problems or convincing myself they can be resolved even as situation after situation piles up as evidence that the real answer is simple: This isn't working.
Y'see, "simple" doesn't mean "easy". Abandoning hope for a valued relationship is never easy. You also never want to do it too soon. I believe that I owe it to myself as much as to my friends and lovers to hang in through difficult times. However, there have been times when I have heard myself complicating and recomplicating a story to explain why things are going to work, and that's when I need to seriously think about K.I.S.S.