2. One spouse refuses to try.
Some marriages encounter damaging, seemingly insurmountable problems—such as infidelity, the loss of a close family member, or a long sexual drought—and rebound from them. But, says Alisa Bowman, author of Project: Happily Ever After, if one spouse repeatedly brings up an issue, asks for help, and makes it clear that the marriage will not last unless they both commit to solving it, and the other spouse refuses to go along, the marriage is in trouble. "One partner can't do all the trying on his or her own," says Bowman. "You can't go anywhere like that." A good rule of thumb: If it's been a year with no progress, it may be time to call it quits.