From my Baltimore Catechism:
Q. 476. Is grace necessary to salvation?
A. Grace is necessary to salvation, because without grace we can do nothing to merit heaven.
Q. 477. Can we resist the grace of God?
A. We can, and unfortunately often do, resist the grace of God.
Q. 478. Is it a sin knowingly to resist the grace of God?
A. It is a sin, knowingly, to resist the grace of God, because we thereby insult Him and reject His gifts without which we cannot be saved.
Q. 479. Does God give His grace to every one?
A. God gives to everyone He creates sufficient grace to save his soul; and if persons do not save their souls, it is because they have not used the grace given.
Q. 480. What is the grace of perseverance?
A. The grace of perseverance is a particular gift of God which enables us to continue in the state of grace till death.
Q. 481. Can we merit the grace of final perseverance or know when we possess it?
A. We cannot merit the grace of final perseverance, or know when we possess it, because it depends entirely upon God’s mercy and not upon our actions. To imagine we possess it would lead us into the sin of presumption.
Q.** 482. Can a person merit any supernatural reward for good deeds performed while he is in mortal sin?
A. A person cannot merit any supernatural reward for good deeds performed while he is in mortal sin; nevertheless, God rewards such good deeds by giving the grace of repentance; and, therefore, all persons, even those in mortal sin, should ever strive to do good.**
Q. 483. Does God reward anything but our good works?
A. God rewards our good intention and desire to serve Him, even when our works are not successful. We should make this good intention often during the day, and especially in the morning.