Listen to some music.
Go with whatever makes you sing and dance. Music helps relieve depression, and it's hard to be sad when you're belting out a favorite rock song at full voice. Music gets you up and moving, and that's half the battle.
Bake a cake and visit an elderly neighbor, serve a meal at a homeless shelter, or supervise a kids' play group to give the other moms some free time. You'll be too busy to brood, and you'll come away feeling grateful for the good things in your life.
Play with a dog.
Dogs don't really have bad days, and they are always up for fun and adventure. A dog and a tennis ball are the perfect antidote to the "poor me" syndrome.
Have some laughs.
Go to a funny movie or play a favorite DVD -- one that always tickles your funnybone. So what if you've seen it a dozen times? If it makes you laugh out loud, it's an excellent choice. The Birdcage and The Great Race may be corny, but they never fail to produce fits of giggles.
Take a shower.
Wash your bad day away. While you scrub your body and hair to remove the grit of the bad day, imagine that you're washing away the crummy feelings. A long hot shower will leave you squeaky clean, right down to your psyche. Afterward, pamper yourself by smoothing rich moisturizer on your damp skin, and relax with a favorite beverage.