Given that repentance is vital to the Christian in a world where men are weak and temptations are many and strong,
more needs to be said on the subject.
Repentance is a psychological act that is made possible - in other words it is made effective - by the Atonement of Jesus Christ.
If it was not for Christ, then repentance would be merely a state of mind, or a change of mind; but because of Christ it is made effectual - because of Christ, repentance saves.
Humans have Free Will, that attribute does not depend on Christ, but the main, the primary function of Free Will is to repent.
Everybody, in every situation, is able to repent if they choose. And every act of repentance will be effective in negating the spiritual consequences of error, failure, weakness, sin, exhaustion, gullibility... everything.
The set-up is that we can always repent everything; because of Free Will repentance simply cannot be stopped or prevented by any power on earth, and because of Christ it is always effective.
This is each person's ultimate invulnerability against the world. And it was necessary that each person be so powerfully protected in order that earthly mortal life be 'a risk worth taking'.
If it were not for repentance, it would be better not to be born as incarnate mortals - but simply to be spirits in Heaven; because without repentance we would have near-zero chance of getting through life without becoming much worse than we began it, and would be be almost certain, after we died, to make the disastrous choice of pride, rejection of God and Hell.
But, by sending Men into mortal life equipped with repentance, which is Free Will weaponized against sin by Christ - this evil fate was prevented; unless after death we actively-choose Hell through refusal to repent that which we know is sin.
Christ made this defence for us by his life, death and resurrection; and he made it for everybody (including those who lived before Christ).
Repentance works for everyone in all circumstances - including those who have never heard of Christ.
What then is the point of telling people about Christ, what is the point of being Christian?
The first answer is that if we know about Christ it ought to make us better at, and more thorough about, and less resistant to repenting.
If we know how the world is set-up - that ought to be a help.
(Of course, sometimes, self-identified 'Christianity' becomes distorted and corrupted, and makes matters worse not better. For instance 'liberal Christianity' which denies the need for repentance of some sins; which indeed encourages pride in some sins is worse than 'nothing' - i.e. worse than Man's natural, spontaneous, 'animistic' religion.)
The second answer is that repentance, although essential, is not the end of the matter.
Living life is also about theosis, sanctification, spiritual progress or 'divination' - in other words, mortal earthly life is an opportunity to grow-up, mature and become more god-like - which is our destiny through eternity.
But, for us mortals, that glorious work and privilege only comes on the other side of repentance; only comes if our safety through life is assured by repentance.