First post here. Haven't played yet, but have been doing some white-room character design in preparation. The Realms of Power books made me wonder...
Realms of Power: the Infernal page 103 says that a curse with the duration "Forsaken" lasts until the the character seeks repentance. In Mythic Europe, this would probably happen by going to a confessional. For a Hermetic magus this poses a significant problem. A confessor who hears the magus' story will probably request that the character humble themselves and stop doing magic, and for how many player characters behave, this is a completely justified reaction. For the players themselves, however, this effectively means retiring the character (unless they want to play out decades of quiet monastic life). Now here's the rub; I don't believe there is a way to weasel out of this.
Magi of lineages such as Bonisagus or Tremere could argue that their magic is secular and thus not the same summoning that the Bible forbids. Their power comes from nature itself, they say, and not some pagan entity. The issue with this is twofold; arguing with God is the height of hubris, and the confessor is unlikely to care. If they say no, it MEANS no.
Someone like a mage Tytalus might just lie and continue doing magic anyways, but God is... fairly likely to notice. Then again, this is the House that takes in lepers, so these magi are likely to declare sour grapes and insist their curse is some sort of challenge.
Some of the mystery cults like Bjornaer and Criamon have already twisted themselves into Gordian knots adjusting their beliefs into a Christian heterodoxy. Bjornaer magi consider their Heartbeast to be the "spirit" third of the Holy Trinity next to their body and soul, while Criamon theories are all over the place but usually place God as the creator and Jesus as the prophet. Again, a confessor who hears one of these explanations would probably dismiss it as a lousy excuse at best and heresy at worst.
The few magi likely to pass a confession are either Holy Magi or a magus willing to restart at a significantly weakened square one with Holy Magic. The question at this point is wether God allows this to count as giving up magic, which would depend on the Game Masters' decision.
Personally I would consider a magus retiring to seek forgiveness for something which isn't even their fault... to be an interesting story and a valid conclusion to a character arc, one I would allow to happen to my character. Other players might not be so patient, and would prefer to get back to playing the game without their character being permanently bushwhacked. So I ask the members of the Arts Magica forum; as a Game Master, how would you let your players break a Forsaken curse? Is this grounds to retire a character, a reason to spend a season or two on a quest for forgiveness, a detail you'd deal with off screen so the game can continue, some fourth thing? All answers welcome.