The Greek word for saint--hagia--means "holy." And so, by definition, a saint is not merely an exceptionally good person, but rather someone who possesses the fullness of the Holy Spirit. Such a person will--naturally--love God above all created things, and likewise he will love his neighbor as his very own self. Having taken up his cross and followed Christ, the saint has ceased to exist as an ego-centered entity, and so he can say with St. Paul, "It is no longer I who live, but Christ in me."
A saint is, therefore, the proof and confirmation of our Faith. The most logical and persuasive argument concerning the existence of God will not convince the skeptic, but a saint--by his or her very life and example--bears living witness to those truths revealed by Christ and preserved in the Holy Tradition of the Church.
That is why--for us ordinary Christians--the Lives of the Saints are so inspiring and edifying, and the reason why the veneration of the saints holds such a central place in the ongoing life of the Church. The truth is, we are all called to be saints, to become gods by grace, transformed and deified by the life-giving power of the Holy Spirit. This is the whole purpose of the Incarnation of Christ and the founding of the Church on the day of Pentecost.
Od course, striving for the ideal of sanctity involves a life-long struggle against the sinful passions, and the willingness to endure sacrificial suffering on Christ's behalf. There is, therefore, no place for the Protestant idea that "Christ has already done it all." Of course, in the ultimate sense, He has, but we are, nevertheless, called to become co-workers with God in the great work of sanctification--not of our own souls only, but of the entire created universe. Let us pray ceaselessly that we may prove worthy of such a high calling.