Do go into the holiday season with a weight-gain plan: Either choose to enjoy going crazy, knowing you'll have to lose 5 to 10 pounds in the new year; or decide to go a little less crazy, and plan on dropping 2 or 3 pounds come January. If you can't bear the thought of having to diet, commit to being strict during the holidays—but remember, it's your choice.

Don't attend events that bring out the worst in you. If you've had (and regretted) a fling at the last one or two holiday parties, maybe sit out the next one.

If something does happen that you wish hadn't, forgive yourself, learn from it, resolve to do better, and move on.

Do take turns with friends as designated drivers if you enjoy drinking at parties. Or, if you can afford it, hire a cab or limo.

Don't go to a party hungry. Eat some soup or fruit salad first.

Don't give up your workout. Exercise is one of the best ways to relieve stress.

Don't skimp on sleep either—you'll feel cranky and less able than usual to deal with stress. (If you're staying up late, try to get a few extra zzz's in the morning: Throw your hair into a ponytail instead of blow-drying it, or skip reading the newspaper.) Regular insomnia and oversleeping are signs of depression. A counselor or therapist can help.

Do plan holiday get-togethers that incorporate fitness, such as sledding parties, snowball fights or long walks with friends.