I'm not sure what church you're part of OP, but the best answer I can give you is that in earlier centuries ctb was seen as both a mortal sin and one creating scandal, and so it was believed that people who ctb'ed couldn't go to heaven.
Today though the view of ctb is a lot more nuanced - it's still considered a sin, but it's also recognized that people who actually go through with ctb are usually not in a healthy state of mind - so many people who do it have clinical depression, for example - which diminishes their responsibility for ctb. Also, repentance at the very end of one's life, i.e. at the very last moment, is still repentance.
The view today generally is that it's possible for people who ctb to be saved thanks to divine mercy, and the above circumstances, but you really can't say for sure.
At any rate, I hope you stay with us.
Who then shall separate us from the love of Christ? Shall tribulation? Or distress? Or famine? Or nakedness? Or danger? Or persecution? Or the sword? But in all these things we overcome, because of him that hath loved us. For I am sure that neither death, nor life, nor angels, nor principalities, nor powers, nor things present, nor things to come, nor might, Nor height, nor depth, nor any other creature, shall be able to separate us from the love of God which is in Christ Jesus our Lord.
- Romans 8:35-39 (Douay-Rheims)
