My patience is the shortest (and thus yelling ensues) when I am engrossed in something that is important to ME, something I want to do for ME, and the kids start fighting or need something (that they can easily do themselves and don't need me for) and I can't get MY stuff done. I am trying to do too much. It helps me to just know that between the hours of approx 7am to 8/9pm I should not try and pour myself into anything else that requires all my attention. Then I am not setting myself up for frustration.
On one hand I feel like I'm never going to be able to do anything for myself, but on the other hand I know that right now during this phase of life I am pouring myself into my little ones and will have time later on down the road for personal time.
Just the way it is right now. And they are worth it.