I wouldn't discount it just because it doesn't rhyme.
I am not sure about whether the quote should be more appropriatly attributed to Theodore Geisel as opposed to Dr. Suess as this is probably from a work meant for an adult audience, either an autobiography or an article on the subject.
However, this quote isn't listed in a list of marriage related quotes take from a Biography of Mr. Geisel here:
http://marriage.about.com/od/thearts/a/tedgeisel.htm
So perhaps it is apocraphyl. I find it attributed mostly to "Dr. Seusss" on the web and not Theodore Geisel so I am inclined to think it is apocryphal, however I am not sure why one would attribute a non rhyming quote to Dr. Seuss.
Likewise, no quote I find lists its original source, such as a biography.