Olympia, Washington (CNN) -- The news that Al and Tipper Gore are breaking up after 40 years of marriage has generated an outpouring of emotion. Although we don't have -- and shouldn't seek -- the inside details, the couple says the decision was mutual and the process will be mutually supportive. Friends have told journalists that no third party was involved; the two simply grew apart.It leads couples to wonder: "Could this happen to us?" or "Could it already be happening to us?"