What was the rockiest part of your relationship, or marriage, and how did you get past it? Or how didn't you get past it?

While reading some past fluther questions, I came across a piece of information that I found to be quite interesting. I can’t seem to re-find the question, but in summary, it is about how after years into a long term relationship, one partner (usually the female, or so I seem to be directed into believing), becomes non interested in sex, which seems to be a horrible pain for the male (in a heterosexual relationship).

So, I was just curious, what are some of the most rockiest situations you have been through in your marriage, or relationship, and what did you do to solve it, or, in the case that it wasn’t solved, what do you wish was done in order to find the correct solution?