[quote="baltobetsy, post:2, topic:84124"]
In this context, "participating in the Eucharist" means going to Mass. You should always receive Holy Communion with the utmost care, which includes making sure you are in a state of grace and fasting for the prescribed hour before receiving (not necessarily an hour before the beginning of Mass, although many choose to do it that way).
So, if you are in mortal sin, or you have not fasted, please do go to Sunday Mass, but also refrain from receiving Holy Communion. This is the right thing to do, not a sin at all. Because almost everyone in the entire church receives Communion at every Mass, some people become confused and think it is obligatory to receive, which it is not.
I would like to correct baltobetsy, you must not go to Mass while in the state of mortal sin. Here is a link to prove it: catholic.com/quickquestions/can-someone-who-has-committed-a-mortal-sin-receive-communion-if-he-makes-a-perfect-ac
Note: You cannot recieve the Body OR Blood of Our Lord or celebrate Mass while in the state of mortal sin unless there is a grave reason AND there is no opportunity to confess your sins.