As Jesus said, when He cured the Roman centurion's slave, "Many will come from east and west and sit at table with Abraham, Isaac, and Jacob in the kingdom of heaven, while the sons of the kingdom will be thrown into the outer darkness; there men will weep and gnash their teeth." (Mt. 8:11-12, RSV)
To me, the bottom line is that we don't know whom God has chosen for the Kingdom, because He doesn't want us to know.
I try to keep clear of mortal sin, go to confession when I fail (and even just in case), and stay right with God. That's all I can do, other than Standing On the Promises, as we used to sing occasionally . . .