In your opinion, what is the most difficult thing a parent has to do?
Die to self. It's the most difficult thing a parent, a spouse ... any Christian has to do. A childhood and young adulthood is spent finding autonomy then to overcome loneliness the young adult finds a mate to "be happy". Then children come along. If there is no reason (I.e. "I love God and my family for love of God") to put self in last place it's a miserable road for all.
This scenario is especially true in America where we are so spoiled; things are readily available. Venerable Fulton Sheen once said something along these lines, "Things are to be used and people are to be loved. We get into trouble when we love things and use people."
If God calls you to parenthood, teach your children about true Christianity early. Learning to die to self early can only help in their future vocations. You, my children, are well on your way.
Dying to self. Learning to serve. Loving. That is the hardest thing anyone - in any walk of life - has to do. Lord, help me love as You do!