Many today believe that all future sins are forgiven. That is not how it works. Paul pointed this out directly in Romans 3:24-26 that the sins that are forgiven are those that are past and not those of the future.
Being justified freely by his grace through the redemption that is in Christ Jesus: Whom God hath set forth to be a propitiation through faith in his blood, to declare his righteousness for the remission of sins that are past, through the forbearance of God; To declare, I say, at this time his righteousness: that he might be just, and the justifier of him which believeth in Jesus.
Ezekiel on many occasions pointed out that the soul that sinneth it shall die and he did so most specifically in the 18th chapter, verses 4 and 20. If this is the case then a sin must first be committed in order to warrant death. People are not held responsible by God for things that they have not done. Repenting one time in life is not an open license to commit future sins. You cannot find anywhere in the Bible that states that a person's future sins are forgiven but we do have Paul, as noted above, telling us specifically that it is the past sins that are forgiven.
What many believe is essentially the concept of putting Jesus up on the cross over and over again in in an open shame as noted in Hebrews 6:6.
If they shall fall away, to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame.
Living a sanctified life separated from sin is not a revolving door of sin just because someone at one time in their life repented and turned to Jesus.
Enduring unto the end is what one must do to be saved and that does not include sinning along the way. Jesus said this Himself, “But he that shall endure unto the end, the same shall be saved”. Matthew 24:13 (see also Mark 13:13).
So contrary to popular modern belief, saints are not sinners and sinners are not saints. Today’s doctrines with which many today subscribe to state that there is such a thing as a sinning saint. The Apostle John clearly stated that this is not the case.
Whosoever abideth in him sinneth not: whosoever sinneth hath not seen him, neither known him. Little children, let no man deceive you: he that doeth righteousness is righteous, even as he is righteous. He that committeth sin is of the devil; for the devil sinneth from the beginning. For this purpose the Son of God was manifested, that he might destroy the works of the devil. Whosoever is born of God doth not commit sin; for his seed remaineth in him: and he cannot sin, because he is born of God. 1 John 3:6-9
Sin is the exception for a believer and not the norm. Too many people today have “when” substituted where it states “IF we sin” in 1 John 1:9.
IF we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.