I am really loving all the responses on this thread, but unfortunately I think I have everyone beat on this subject.
In 1999 I went with my family, which consisted of me, DW, DS1 1/2, MIL, FIL, and 3 younger BIL's. I was 22 years old, my wife and I had been married for just around a year and a half. We stood in the tree houses at Disney Institute for 5 days. It was going to be an awesome trip, or so I thought.
On the first night there, my wife told me that she was moving back home with her parents when we got back. She was leaving me!!! At the time, I was shocked and completely confused. So I spent the next 4 days feeling like a complete idiot, because it was me and her whole family there the entire time. She told me that if she came home after the trip, it would be too hard to leave. Let's just say for that trip WDW was not the happiest place on earth.
Luckily it did not ruin my love for Disney, and I made my next trip with my new wife and daughter 6 years later. And, the magic returned. We are going again this February.