A female egg fertilized in the womb must grow into an embryo, a fetus, and then a full born baby, otherwise it will die. An acorn seed planted in the soil must also grow into an oak tree, or it will die, because it cannot remain as a seed. Similarly, everyone who is in the kingdom of God must commit themselves to spiritual growth.
If you commit to growing spiritually in every area, it will be impossible for you to fall out of the kingdom of God. If you see negative qualities and characteristics in others who have been raptured into the kingdom of God, inspire them to change by speaking the truth in love. In doing so, you will prevent their hearts from becoming calloused and hardened.