To receive a partial indulgence, you have to recite the prayer or do the act of charity assigned. You have to be in the state of grace at least by the completion of the prescribed work. The rule says" at the completion" because often part of the prescribed work is going to confession, and you might not be in the state of grace before you do that. The other thing required is having a general intention to gain the indulgence. If you perform the required act but don't want to gain the indulgence, obviously you won't gain it.
An indulgences is defined as "the remission before God of the temporal punishment due for sins already forgiven as far as their guilt is concerned." The first thing to note is that forgiveness of a sin is separate from punishment for the sin. Through sacramental confession we obtain forgiveness, but we aren't let off the hook as far as punishment goes.
Indulgences are two kinds: partial and plenary. A partial indulgences removes part of the temporal punishment due for sins. A plenary indulgence removes all of it. This punishment may come either in this life, in the form of various sufferings, or in the next life, in purgatory. What we don't get rid of here we suffer there.
The requirements for a plenary indulgence are tougher than for a partial. After all, a plenary indulgence remove all the temporal punishment due for the sins committed up to that time.
(If you sin later, of course, the temporal punishment connected with the new sins isn't covered by the earlier plenary indulgence, but, at least thnishment for the old sins isn't revived.)
"To acquire a plenary indulgence," says the Enchiridion, "it is necessary to perform the work to which the indulgence is attached and to fulfill the following three conditions: sacramental confession, Eucharistic Communion, and prayer for the intention of the Sovereign Pontiff. It is further required that all attachment to sin, even venial sin, be absent."
The Toughest Requirement
The greatest hurdle is the last. Making a good confession is not particularly difficult, and going to Communion and praying for the Pope's intentions are easier still. It's being free from all attachment to sin that's hard and it's quite possible that even evi-dently good people, who seek plenary indulgences regularly, never, in their whole lives, obtain one, because they are unwilling to relinquish their favorite little sins.
There is an account of St. Philip Neri, who died in 1595, preaching a jubilee indulgence in a crowed church. A revelation was given to him that only two people in the church were actually getting it, an old char-woman and the saint himself. Not exactly encouraging, huh? But don't worry. If you aren't perfectly disposed and can't get the plenary indulgence. you'll at least come away with a partial.
It should be pointed out that the first three conditions may be fulfilled several days before or after doing the prescribed work, through receiving Communion and praying for the Pope are usually done the same day the work is performed.
By the way, the standard prayers for the Pope are one Our Father and one Creed, though you're at liberty to substitute other prayers.