The historical purpose of the Lenten period is repentance, but the relevant question might be, “repentance from what?”
The obvious Christian answer is that we repent from our sins of commission and omission, confessing to our God and our fellow people that we continuously fall short of our responsibilities to them. This answer is applicable whether or not we believe in Christ as our savior because of the conviction of our own consciences. The only way to avoid such conviction is if we delude ourselves into believing we are not doing such things at all.
And if such an answer is applicable regardless of what we believe about Christ, then the next question we have to ask is what about Christ? If we know we sin, then we cannot do right by ourselves. If we admit we cannot do right by ourselves, then we understand we need a savior. Christ is that savior, the one who paid the price we could not pay for the things we cannot stop doing wrong.
Christ came to earth with a simple message: love God with all of your heart, mind, and strength and love your fellow people as yourself. Yet, he understood we could not do this ourselves, so he offered something else instead: he would do those things for us and all we have to do is have faith in who he is and why he did it. Even better, he promises to give us that faith because he knows we are not even strong enough to believe on our own.
Lent, then, is a time for us to consider this state of affairs. We have a simple law, so simple that it is heartbreaking to consider how many times we failed at it just today. We are lost and we need rescuing, but we know that a rescuer has already come and offered us redemption from what we have done wrong.
So, if we are sinners in need of a savior and that savior has already come and promised us redemption, then all that remains is to look upon that savior as he presents himself in his word and cry out to him with the words he has already given us to say with the faith he has already given us to save us: “Christ, have mercy on me a sinner.”
Now, knowing that we are already saved, and having concentrated ourselves on the nature of our salvation, we can turn ourselves to living the life of loving God and our fellow people as Christ wants us to live. Repentance becomes liberation, and it is that liberation that Lent prepares us for.