a) What is holiness or the fullness of Christian life?
Holiness or the fullness of Christian life is union with God to become like Christ. It means doing our best to become better persons, to imitate Jesus, to become perfect as our heavenly Father is perfect, with the help of the Holy Spirit.
In Baptism God calls us to go to heaven and be with him, that is, to become saints. The means for this include our prayers, the sacraments, and studying his teachings, which we apply in our daily life by doing our duties well and helping others.
b) How can an Altar Server strive for holiness?
To attain holiness we must love God above all things and our neighbor as ourselves. This way we do everything out of love of him.
The Altar Server’s “ordinary duties,” which he should do well and offer to God, include among others his prayer, study, household chores, serving the Mass, recreation, helping friends in their studies and in their work. He need not wait for special or extremely difficult occasions to show his love for God and his neighbors.