I'm fairly certain that many a Catholic over the years has probably slipped up and taken the Eucharist even when they knew they were in a state of mortal sin. I have done it for a variety of reasons. I may have simply been afraid to go to confession, been embarrassed to skip communion, been unable to attend confession for some reason, or I may have been filled with such a desire to have the Eucharist that I ignored my conscience and ate of the sacrament anyway. I am aware that at all of these times I committed a terrible act of disrespect and that God is unhappy with me for it.
However, I have never been clear on what exactly this act "is". I have never heard of it called a mortal sin, even though on occasion I have confessed it at reconciliation. Is this sacrilege something you confess? Is it something god cannot forgive?
To broaden the discussion a bit, to what extent is a priest held responsible for it? I would be willing to bet that there are times where a priest needs to go to confession, but it's not as if he can simply skip mass on the excuse that he is unclean and unable to have the Eucharist.