A prominent U.S. journalist recently wrote a book describing how she "hates" her husband, but has no plans to divorce him. And while "hate" is an awfully strong word, what it really speaks to is how no marriage is perfect...not even close. Even within the strongest of unions, there are days where dislike and annoyance far overshadow affection and love, and that can actually be quite healthy. But when is it not? Here's how to tell the difference.