But what about “backsliding” and “stumbling”? You’re not “unborn”, but you do run the risk of rejecting the grace given at baptism . . . .
What? Everybody backslides and stumbles, that exactly why Christ's death was the santifiying act for all of us to satisfy God's decree. Look, it is more simple than you or I could probably imagine, but if you are born again spiritually then you are an inherited child of God and NO ONE CAN SNATCH YOU OUT OF HIS HAND, period. End of story. You are eternally saved.
Those who think you can lose you're salvation always use this irrational logic about continued sin, and I believe these same do not understand grace properly. Those who think you can lose salvation completely disregard Christ's message about building up good things for heaven. If you're going to be irresponsible or take advantage of your salvation, then you probably will here about from DAD in heaven! The good thing is he will always be your DAD, no matter what trouble you try to get in too and you will forever have a home waiting for you.
The question Christians who wilfully sin need to ask themselves is, not how am I going to live away from God in my sin, but rather how am I going to live WITH him in my sin, because he isn't leaving, and you aren't getting away...