Parenting is the toughest job in the world.
Why?
Well, for one thing, parenting is a job you can never truly master. By the time you figure out one stage of life, your child has already moved on to the next one, and you have to start all over.
For another thing, you can never quit. You will come to the end of yourself regularly and often, but somehow, someway, you have to keep going. That small person depends on you, and God has entrusted him or her to your care.