If I could go back and talk to myself when I was a mother with young children, this is what I'd say:
Take a nap!
There is absolutely nothing that you can do during your very little free time that is more important than resting.
Lack of sleep messes a person up, it alters their chemistry, makes them moody, and ill-tempered. You are a person. You are not immune from the effects of sleep deprivation. Go to sleep, or close your eyes and breathe deeply.
Nothing is more important.
Also, everything is a stage, and it will pass.
Now, go lie down.