56 Q. If one has only venial sins to confess, must he be sorry for all of them?
A. If one has only venial sins to confess it is enough to repent of some of them for his confession to be valid; but to obtain pardon of all of them it is necessary to repent of all he remembers having committed.
57 Q. If one has only venial sins to confess and if he does not repent of even one of them, does he make a good confession?
A. If one confesses only venial sins without having sorrow for at least one of them, his confession is in vain; moreover it would be sacrilegious if the absence of sorrow was conscious.
58 Q. What should be done to render the confession of only venial sins more secure?
A. To render the confession of venial sins more secure it is prudent also to confess with true sorrow some grave sin of the past, even though it has been already confessed.
59 Q. Is it well to make an act of contrition often?
A. It is well and most useful to make an act of contrition often, especially before going to sleep or when we know we have or fear we have fallen into mortal sin, in order to recover God’s grace as soon as possible; and this practice will make it easier for us to obtain from God the grace of making a like act at time of our greatest need, that is, when in danger of death.
Catechism of Pope St Pius X.
72 Q. What sins are we bound to confess?
A. We are bound to confess all our mortal sins; it is well, however, to confess our venial sins also.