If you are in a state of sanctifying grace then a certain amount of merit is acquired through pious acts. The good angels help us to remain free from sins, perhaps through mental reminders that one is not aware of, because they are pure spirits. Everyone has a guardian angel.
The following prayer is a prayer that can be used to obtain a partial indulgence, No. 18:
A partial indulgence is granted to the faithful who devoutly invoke the care of their guardian Angel with a duly approved prayer (e.g. Angele Dei)
Angele Dei
Angel of God, my guardian dear, to whom his love entrusts me here, enlighten and guard, rule and guide me. Amen.
No need to pray it three times. St. Michael will help you by the grace of God, as all the saints and angels do when we pray to them. In particular, St. Michael can be powerful to call on when we feel the presence of evil.
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