One of the things the discipline of Lent teaches us is that we don't believe in magic.
Fasting, abstaining from meat, denying ourselves certain legitimate pleasures in order to strengthen ourselves against temptation, spending more time in prayer and Scripture, making reparation for sin by concrete acts of charity -- all of this and much more flows from the conviction that God's forgiveness does not take away our role in repairing the damage done by sin.
Sin destroys a fourfold set of relationships: our relationship with God, with others, with creation, and with ourselves. Even when we mess things up like that, God loves us as we are. Yet he also loves us too much to let us stay the way we are. He calls us to repentance and reform. Repentance, whereby we see the evil of sin and resolutely turn away from it, is a gift. We can't presume upon it. I'll always remember the time someone asked me whether he could confess a sin before committing it. The answer is no, because if we intend to commit the sin, we are obviously not repenting, and we cannot presume on the grace to repent. We need to ask that grace now. "Of forgiveness be not overconfident," Scripture tells us. "Delay not your conversion to the Lord" (Sirach 5:5,8).
Once we do respond to the gift of repentance and receive forgiveness, there is still work to be done. God's forgiveness is not a magic wand that removes all the wounds of sin and bypasses our need to freely cooperate in healing those wounds. This is precisely where penance comes in. Penance -- and Lenten practices -- are meant to strengthen the fourfold relationships that have been harmed by sin. If, indeed, we are serious about turning away from sin, we have to work in some fashion to repair the harm sin has done.
I have seen vivid examples of the willingness to do this in the work I have done with doctors who used to perform abortions and no longer do so. They know that what they did was wrong, and they have sought and received God's forgiveness. But that does not bring the babies back to life, nor does it heal the wounds -- physical, emotional, and spiritual -- that abortion has inflicted on the mother, the father, and many others, including the doctor.
Therefore, as part of the realistic effort to repair the damage of sin, a number of these doctors have made the resolution to seek out the women on whom they have performed abortions -- and apologize to them! They even go further and make this offer to those women: "As you may know, abortion carries many physical and psychological aftereffects. If you are experiencing any of these, and need treatment, I will assist you to obtain such help."
There's the spirit of Lent. We respond to the love of God; we don’t presume upon it. We receive His mercy, and then we go to work!