a) What is penitence?
Penitence is the virtue that leads us to be sorrowful for having sinned and for being sinners. It includes the willingness to make up for the wrong done, through prayers, mortification (or sacrifices) and good works.
The more we love God, the more we realize the evil of sin. Even though we repeatedly reject God through the same faults, he does not hate us in turn. Rather, like a loving Father, he awaits our return if we are sincerely contrite and strive not to fall again.
b) Why should Altar Servers live the virtue of penitence?
God respects our freedom and does not force us to avoid sin or to return to him. In the same way, if we die in the state of mortal sin, God will not force us to be with him in heaven. In this case, we have chosen to go to hell instead of heaven.
We make up for our sins and those of others by offering prayers and sacrifices to God, telling him how sorry we are for having offended him. We should also go to Confession frequently and regularly, and as soon as possible if we commit a mortal sin. Let us make a sincere Act of Contrition for our faults when we examine our conscience every night before going to bed, and make a firm resolution not to commit them again the following day.