The Bible is the paperwork God filled out to complete our adoption. It says that once we have accepted His offer to adopt us, He will never give us back. It cannot be undone. There is no ambiguity about this. Our adoption by God is unilaterally irrevocable. He will never forsake or abandon us, even if (when) we try to forsake and abandon Him.
If you already know your mission, what's going to get you where God wants you to go? Or if you don't know it, what should you do? Consider Jesus. God sent His Son to build a team of men to accomplish His mission. It worked. Never before or since have so few impacted so many.