What advice have you heard or tried that was just flat-out wrong?

I was advised by a group therapist, when having "cold feet" about commitment in a relationship, to just think about how bad the alternative might be. She had a friend who had reservations about getting married, and then thought not getting married would be stressful too, so she went ahead with the marriage. It was terrible advice, especially from a therapist providing guidance for some very troubled people. The only good reason to commit to a relationship is because you really want it, not because you're afraid of what will happen otherwise!