Heaven and Earth is the spiritual and the physical. That is why the very first word sin the Bible concern these two. Everything focuses on that in the Bible. The two parts of us were made to work together, but we know that as Christians, the earthly part of us gives us trouble still. Heaven did not change.
Earth is the problem.
You cannot simply leave your flesh alone and expect all to turn out alright. One sinner man told me he did not think to take his child to church since he would let the child grow and the child would make up his own man later in life. If you as a parent le the child go and let his flesh have its way and not direct the child to understand about God and the spiritual, that flesh will go wild. The child will only by a miracle later choose. Jesus compared our hearts to the soil.