You just do what you can. I tried to keep the routine as close as possible to what it was, kept the familiar things nearby, and if it meant the housework didn't get done then so be it.
The hardest things I have found are a) bathing the girls. Sometimes I need 4 hands!! b) Nights of no sleep (the girls have been sick recently) and then days with grumpy kids as well, so no break for days at a time. In the end I let the girls run wild throughout the house while I had a snooze on the couch just to try and function - they could get to me, I could see them wherever they were, and they couldn't get into trouble. I am lucky that their dad has them on the weekends, so I do get 2-3 nights a week to catch up on my sleep.
The boys mayyyy react by not sleeping as well (the girls have, especially Amber - she frequently ends up in my bed because she wants to be near me all the time). It's something that you really have to go with the flow for. One thing I WILL suggest - make sure you have some easy meals in the freezer for those nights where nothing goes to plan. Sometimes it's been 9pm or later before I've been able to have my tea, and by that time you a) don't want anything heavy and b) can't be bothered cooking anyway.
I do most of the housework and my study either at night or when they are asleep throughout the day.
The girls don't seem to really miss their dad much though, and I gather they don't miss me too much during the weekend - it's not until they see each of us again that they remember that they love their mummy/daddy