A saint is someone in union with God. He is completely obedient to the Lord and thus free of the world. We may not be saints yet, but it does't mean we cannot become saints. Surely God would never tell us that we are holy enough for him now nor that we are not good enough to become saints. The fact that Jesus tells us to be perfect as the heavenly Father is perfect shows that he wants us to be saintly and that it's totally within our reach. To succeed in becoming a saint, we need to know in theory that we must let God truly be our God and follow in practice by yielding ourselves to God. The sooner we do it, the greater our reward in heaven will be.