If salvation can be lost (or thrown away), then there must be something you must do to lose it.
If there is something you must DO to lose your salvation, then there MUST be SOMETHING you must do to maintain it.
If you must do something to maintain your salvation,
then salvation is not a gift... period.
You cannot have it both ways.
You either belong to God, or you don’t.
If you belong to God, then you no longer have the choice to not belong... because you gave up that choice when you received Him.
You can certainly chose to throw away your mortal life... but not your eternal soul.
Once God finishes what He started, and the process of salvation is completed in our resurrected incorruptible bodies, THEN... (maybe) we can chose to throw it away again after that.... but even that I doubt as being possible let alone desirable.
There's that DO again...
It is indeed a gift; but any gift can be rejected.