There is a fundamental difference between the Arminian concept of “once saved always saved” and the reformed concept of “perseverance of the saints”. Both conclude that salvation cannot be lost but differ at a basic level regarding the foundation of that truth.
Paul described salvation as a rebirth, a change of heart from the old man to the new man. Continuing to sdin as before salvation is not salvation. Unless the saved perosn is fundamentally changed by the indwelling of the Holy Spirit there is no salvation. It is not a crap shoot. It is a total sacrifice of self to Christ’s redemption. In order for the new man to be born the old man must die.