Another way to understand the verses which seem to exhort believers to continue or lose is to understand, first, the underlying premise that salvation is by grace and is therefore unearned, meaning it cannot be un-unearned; therefore, verses which seem to suggest otherwise are, instead, assuming eternal security and merely encouraging behavior to match.
Or, better or more behavior (there will always be SOME).
Actually... responsible for understanding it.
For that you need a set of appropriate premises. And they are not at all flattering to religionists. We aren’t just not great shakes. We’re terrible shakes. And God’s love is not just passing or fickle. It’s shed abroad from the heroic Cross.
Was Lucifer saved? Yes
Did Lucifer fall? Yes
Until you can reconcile this your doctrine doesn’t exist.