How is the story you're telling about yourself? What do you really think of yourself: as a parent, as a spouse, as a friend, and all the other roles you play?
Your words are your magic wand
Your feelings and thoughts are connected. We like to say that your words are your magic wand. That is, if you're always thinking, Ah, I wasn't patient again, I yelled again, I can't figure out how to be a mother, then you're going to be hitting yourself on the head all the time. When you do that, you give yourself the feeling that you're not good enough, not good at being a mother, and that translates to how you react towards your children with helplessness and frustration.
What you focus on will grow
So you have to work on how you talk to yourself—your inner voice. We often see a strong tendency to pull out a flashlight and shine it right at the problem. We have a little saying, us Viking Moms, that says, "What you focus on will grow." So when you're always focusing on the things you can't do, how you're not good enough, that's what's going to grow; and then it seems like you're hopeless, you're good for nothing, and that one little problem can take up everything.
Start speaking well of yourself
Instead, you have to focus on your successes. Self-care also means speaking well of yourself. That'll leave you feeling good about yourself, and that translates into behaving differently toward your children, too. You have to focus on all the small successes where you're good, where you do well for your children. That's what you'll think about: I can do that well, I've got to do more of that, since I've got a solution in myself. When you consciously start to work that way, you'll see how it starts to change so much inside you, and how it rubs off on your children.