The state of marriage can make people happier even if the particular partner is a disappointment or an irritant. The state of marriage seems to offer security to lives that would otherwise be obsessed with either the deficiencies of the unpartnered state or the search for a partner. The marriage does not have to be very fulfilling to offer comfort and structure and the sense that a life is going on. But when the marriage is threatened, by you or your partner, that's a major threat to the sanctuary of domestic life, and thus a trigger of intense insecurity and disorientation. Obviously, a few marriages are so abusive or degrading or unequal or insecure, they offer no sanctuary at all. Even then, it is rare for people to leave until they have found a potential partner who offers a more hopeful alternative. The human animal resists being alone.