Mat 7:21 KJV Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven.
It is possible to work for God and yet not be of God. Because the first thing over all things is to have God in your heart and do His will
I have seen Men, who in the course of their assignments strayed away, but the grace to complete the assignment still resided in them.
Remember, the bible says many preached, prophesied, sang, etc. Meaning, they might have been in the course of their assignments according to the gifting given to accomplish the assignment.
Check your salvation above all. Work it out with fear and trembling.