The most important thing for me was Day 8 and the true depth of personal communication.
I, at one time, knew most of this stuff, if by other names and other means. My wife and I became very close and could discuss anything without getting too emotional. Since then (and over the last decade or so), we have forgotten how to communicate at that level. While we were still skilled in the good habits of frequency and content for discussions, we had become unskilled in the core details of listening, and truly hearing what was said.
I realize, now, just how much distance there is between us, and will be working on that in the weeks to come. It would be overly dramatic to say this saved my marriage, but it certainly will help reduce the tension and rough spots as we get back to where we should be.