One of my children has walked away from the Lord and it is heartbreaking. I am praying for this child ceaselessly! I gave this child to the Lord as an infant; I cannot take the child back now. God will see them through, but as parent it is hard to watch.
We raise our children to know right from wrong, to believe the Bible as the true Word of God and we have to rest in the fact that is it out of our hands when they become teenagers and grow into adulthood. They will either reject or accept Christ and there is not much to be done by that point. I did tell all my children that while they lived in our house they would be expected to attend church, today I have to wonder if I did the right thing. I may have planted the seed of rebellion.
Above all let you child know that even though you may not like their decisions you love them no matter what. When they decide to return to God your attitude can foster reconciliation – as long as you did not burn the bridges in the heat of the moment. I had to rebuild some bridges on the way to reconciliation with my child as I tried to stay a constant in their life. Hang in there you are not alone, you may not understand what is going on but God does.