During Lent are we supposed to say the Sorrowful Mysteries everyday up until Easter Sunday when praying the Rosary?
This answer may not seem timely (as Lent is concluding); however, the answer I will give is meant to be timely in any moment, as there is merit to considering a more general approach to days for the mysteries of the Rosary and their connection to the seasons of the Church year, within which this submitted question is a specific example.
It is not necessary to pray the Sorrowful Mysteries each day during Lent. In truth, as devotional prayer the Rosary is not subject to strict requirements
regarding the days the mysteries are prayed in the same way that the Mass is bound to the liturgical calendar. That each day is assigned a set of mysteries (which if you remember, St. John Paul II modified in 2002 when he gave us the “Luminous Mysteries”) is to be taken as a way to engage us in praying all of the mysteries regularly, rather than focusing on only one or another set without due regard for the rest. On the other hand, it is fitting to pray those mysteries that
apply to a given feast day or liturgical time, even if it is not the customary day of the week for which the mysteries are designated (such as praying the Joyful
Mysteries on Christmas Day, even if Christmas is not a Monday or Saturday). Therefore, I would encourage a more frequent use of the Sorrowful Mysteries in Lent (or the Glorious Mysteries during Easter) if you are accustomed to praying more than one set of five decades each day. At the same time, I would say for those who pray the Rosary once per day it is fitting to simply follow the recommendations for each day of the week as given.
Are all venial sins forgiven at Mass? If we don’t have a mortal sin to confess how often should we go to confession?
It is understood that the graces of the Mass do forgive venial sins (which, by the way, is another reason why the Penitential Act of the Mass [that is, the “I confess to Almighty God…” and/or the “Lord, have mercy” at the beginning] is so important as part of preparing to offer the sacred mysteries. In addition, the worthy reception of Holy Communion is understood to affect the forgiveness of any venial sins.
On the other hand, I urge you not to see such forgiveness of venial sins at Mass as prevention from regular confession. Though the precept of the Church states that we are to confess our sins “once a year in the case of mortal sins,” that precept is truly the low bar – and it does little to acknowledge the power of God’s love and mercy in a regular way. For even when one has not committed a mortal sin, regular (that is, monthly) confession is a good practice from the point of view of receiving God’s grace to be drawn into deeper love for Him and to have increased grace to be strong in time of temptation. Since the sacrament of confession is a very particular encounter with Jesus’ mercy, it is not sound thinking to believe we do not ever need it simply because we have other ways to manage without it. Thus, while it is true that Mass forgives venial sins in those who are not in a state of mortal sin, might you consider such mercy a regular means to forgive venial sins in keeping with regular confession as both a source of forgiveness of all sins and a further way to be strengthened against sin.