A rule I have had for years is: to treat the Lord Jesus Christ as a personal friend. His is not a creed, a mere doctrine, but it is He Himself we have.
It is a masterpiece of the devil to make us believe that children cannot understand religion. Would Christ have made a child the standard of faith if He had known that it was not capable of understanding His words?
Preparation for old age should begin not later than one's teens. A life which is empty of purpose until 65 will not suddenly become filled on retirement.