How To Avoid The Baby Blues (Or The Toddler Blues, Or the General Mommy Blues...):
Talk, talk, talk.
Find a good friend (preferably a fellow Mama) and talk it out. You'd be surprised how often other Mamas are feeling the same way.
Staying cooped up in your house is a sure-fire way to bring on the sad. As difficult or exhausting or annoying as it may seem, getting out and about will raise your spirits. Call a buddy for a playdate. Go window shopping. Even going to the grocery store can help. Skedaddle and see what happens.
Realize that you are NOT alone.
You probably have other Mama friends who can empathize and, even if you don't, there ARE other Mamas out there who can. Find a blog or a community forum or a meet-up group where other Mamas are talking about the same things. I promise you, there is someone out there talking about it. Whatever it is.
Take a break.
While that may seem impossible at times, there are levels of breakage here. There's the tiny break: baby is crying or toddler is screaming or both kids are tantruming and you JUST CAN'T. Put the kids safely in their cribs and go to the bathroom. Even 5 minutes alone can help. There's the breather break: when your partner gets home or your babysitter arrives, find a way to get 20 minutes to yourself. Take a long shower with your favorite shower gel. Go for a walk. Go get a mocha. Cuddle up with a blanket and read. Finally, there's the much needed, but fairly rare, daylong break: take a day for yourself. It may only happen once a year, so make it good. Do something that truly makes you happy. Hang out with good friends. Go for a spa day. Get a sitter and take a day with your husband. Whatever you do, make sure it helps you relax. It might not happen again for a while. But even if it doesn't, even the tiny breaks can help. TAKE THEM.