I’m very nervous with a penance being done to have “great peace of mind.” One of the doctrines of the Church is that our priests and confessors are our religious superiors, therefore we are to be obedient to them. When they give us an order, we are expected to follow it (unless it is to sin). By saying that you need a stronger penance because the penance that a priest standing In Persona Christi issues isn’t strong enough is (in my opinion) going down the road to serious error.
Perhaps part of the penance is learning to accept the penance that you don’t feel is strong enough. Reminding us that God’s ways are not our ways, and His thoughts are not our thoughts.
That being said, I do not think there is anything wrong with asking for a clarification, or if there are problems with your ability to complete the penance asking the priest for possible assignment to a different penance.
To clarify, my friend (no, it wasn’t me

) did not ask for a different penance than the priest gave, but rather asked for a relatively strong penance in the course of the confession, due to the nature of the sin. With this request the priest agreed and it was helpful for this particular penitent.
I do not have the answers on this, so I’m exploring it with the rest of you. But what is the penance? It is some portion of the temporal punishment that is still due your sins, even though they are forgiven in the confessional. And, speaking generally, does God Himself not give more temporal punishment for more serious sins?
It would seem then, with regard to penance, that generally speaking more serious sins should receive more serious penances, rather than the stock three Hail Marys for everything from telling a white lie to selling hard drugs to kids. The Catholic Encyclopedia says:
As stated above, the absolution given by the priest to a penitent who confesses his sins with the proper dispositions remits both the guilt and the eternal punishment (of mortal sin). There remains, however, some indebtedness to Divine justice which must be cancelled here or hereafter (see PURGATORY). In order to have it cancelled here, the penitent receives from his confessor what is usually called his “penance”, usually in the form of certain prayers which he is to say, or of certain actions which he is to perform, such as visits to a church, the Stations of the Cross, etc. Alms deeds, fasting, and prayer are the chief means of satisfaction, but other penitential works may also be enjoined. The quality and extent of the penance is determined by the confessor according to the nature of the sins revealed, the special circumstances of the penitent, his liability to relapse, and the need of eradicating evil habits. (
The Sacrament of Penance)
But of course there are a lot of variables there in that last sentence. It’s just my observation and I think others probably share this that typically priests give extremely light penances for everything, even for very serious sins, there’s no differentiation at all, and I think this may start to cloud certain distinctions in peoples’ minds.
It is very true too, however, that we humans are extremely prone to thinking that we can work out our own salvation ourselves, if only we work hard enough, so God’s graciousness is an important emphasis as well.
I’m asking the question, not supplying any answers.