Personally, I find it all too easy to feel frustrated or even annoyed when, for example, I have to pay bills (cuz they're due tomorrow) and the kids constantly interrupt me with their needs.
On those days, more than any other, we moms have to remember our calling. Rather than get caught up wondering what great purpose God has in mind for us, we need to remember we already know our two most important callings: Wife (if we are married) and mother.
There is no calling greater than these two. You may think God wants you to write, to teach Sunday School, to work in the church...but if any of these things make you neglect your first two callings, you need to stop.
Stop. Breathe. Remember your calling: To serve your children.
After all, what greater calling can there be than to raise up little people to know the Lord? That's way more important than working in the church, or writing...or paying the bills.