When you have young children, and you are the primary caretaker, I think they must come first. If they don't, I think it will hurt both of you. This is not to say that you should put your writing aside when you have children; rather, it is to encourage you to work around their schedule as much as you can...In order not to cheat yourself, you have to make writing a high priority... But you have to live the rest of your life, too; you have to allow room for all that makes you you, for all that feeds you. In my mind, being more than a writer, means you're more of a writer.
My hats off to other writers who are also full-time moms to young children and manage to get a little work done everyday. I shoot for four days of writing a week, and usually do it. But sometimes life happens and nothing gets done, and then I feel guilty, when really I shouldn't bother feeling that way. Because I will never make the choice of writing over caring for my sniffly daughter, or taking her to get a balloon on a day that she really, realllllly wants one, or lying on the living room floor while she gives me a pedicure with a crayon.