A lot of discussion has gone into what an indulgence really is. Of course, it is NOT buying a chicken bone said to be that of St. Peter (which may or may not have been a serious abuse in the Catholic Church in the middle ages.) Instead, it is the remittance of temporal punishment for sin, and it comes in two forms - plenary and partial. Take a look at this from EWTN. It might be the best discussion of such I have ever seen. It also is definitely not easy, because who can honestly say their heart is completely removed from all attachment or desire for sin?