We receive an increase in sanctifying grace through the Sacraments, especially the Sacraments of Penance and Holy Eucharist. We can make our most ordinary actions merit a heavenly reward by doing them for love of God. We can merit only when we are in the state of grace and perform good works freely with God's grace.
God wants each of us to attain to the degree of glory he has prepared for us in his Kingdom. If we are mindful to do for love of God, the small actions of daily living, the bigger things will fall into place. Jesus said that "a cup of cold water given in my name" will be rewarded. We can make up our own little prayers that will help us unite with Jesus and fullfill his request to do everything with love and so grow in grace, e.g., "Jesus, it is for love of you, please help --- in her pain." The idea is to do our small actions consciously and with love. It"s acceptable to think of others as we make our intention. That often means doing the very best we can, for God, even if no one sees or knows but God himself.It raises the quality of the dialogue we engage in all day, with ourselves, to include Jesus and so we grow in the habit of prayer
To summarize: Sanctifying grace is a precious, free gift from God. It is a participation in God's own life.
