I try to be strong and keep it inside until I can't take anymore and then bawl my eyes out and need a break from the everyday scramble. Unfortunately I have relatives that are chronically depressed and a couple that have attempted suicide, so my DH freaks out every time I need a good cry (which isn't too often but right now I'm pg soooo... lol!). I can't get him to understand it doesn't mean I'm depressed, everyone just needs a good cry once in awhile when things get overwhelming. Having two boys is challenging especially when you're around them 24/7 (I don't have anyone to watch them ever so I can get a break), so I need that cry at least once every couple weeks because I start to feel trapped.
I also agree with others that making lists to accomplish anything (I have a dry erase board I use and it feels great to cross things off the list) helps as well as having those days when you just say "forget it" and let the kids watch TV or play video games more than you normally would just to catch a break. Just dropping what "needs" to be done and going outside or to the park with the kids sometimes helps me realize what's really important, too.