How can Christians sleep at night?

Say you are saved and you believe you will be going to heaven when you die, but one of your children whom you love dearly has denounced Christianity and wants nothing to do with it. How can you take comfort in knowing your beloved child will be burned for all eternity while you are living in comfort? Even after all your begging and pleading, could you really go to heaven and just say oh well I did my best? How could you ever be happy? How can you justify this? It seems very selfish to me.