When a righteous man doth turn from his righteousness...

Prior to the cross obedience was expected just as after the cross.

Obedience shows we are saved (fruits meet for repentance) yet the cross provides the salvation itself.

If you bring bad fruit and that without repentance willingly then you will see yourself forfeiting the gift of salvation provided by Jesus Christ's death on the cross.

King Saul had God spirit taken from him and King David confirmed that this was a potential for him as well in his repentance prayer to God (Psalm 51).

See also Ezekiel chapter 3 where it talks of a righteous man turning back to iniquity and thus dying in his sin.

The Bible equates a righteous man as a saved man and in chapter 3 of Ezekiel it states that if that man willfully turns back to his sin then his righteousness would be no longer remembered and that he would die in his sin.

Again, When a righteous man doth turn from his righteousness, and commit iniquity, and I lay a stumblingblock before him, he shall die: because thou hast not given him warning, he shall die in his sin, and his righteousness which he hath done shall not be remembered; but his blood will I require at thine hand. Nevertheless if thou warn the righteous man, that the righteous sin not, and he doth not sin, he shall surely live, because he is warned; also thou hast delivered thy soul. Ezekiel 3:20-21

All his transgressions that he hath committed, they shall not be mentioned unto him: in his righteousness that he hath done he shall live. Have I any pleasure at all that the wicked should die? saith the Lord GOD: and not that he should return from his ways, and live?  But when the righteous turneth away from his righteousness, and committeth iniquity, and doeth according to all the abominations that the wicked man doeth, shall he live? All his righteousness that he hath done shall not be mentioned: in his trespass that he hath trespassed, and in his sin that he hath sinned, in them shall he die. Ezekiel 18:22-24