The stress of a major event can unleash the inner maniac in men or women who are otherwise calm, collected and considerate people.
Ideally, you have a maid of honor who can be counted on to keep unruly bridesmaids or family members in line if they start to cause trouble. If someone manages to slip through the cracks, however, nip any complaining in the bud by calmly reminding the unhappy uncle or complaining cousin that you're preparing for the most important commitment of your life, so you'd appreciate it immensely if he'd shut his piehole. Do your best to stay zen, and hopefully your aura will rub off on everyone else. If not, put your ear buds in and drown out chatter with soothing music until it's time to walk down the aisle.