grave positive precept...not necessary... to prevent
Someone or some people saw you earlier today do something gravely sinful (grave here unrelated to the grave of the quote). Two hours later, you are about to get in line for communion. Those people are seated behind you a couple rows. You refrain from communion EVEN THOUGH you went to confession and were obsolved of the sin an hour ealier as your conscience got the better of you. They don’t know that you went to confession for this sin. You will not go to hell for missing communion. You will help them not think the Church is a farce if you refrain, in your love for Jesus and their own faith, from receiving Him as you may certainly do.
I remember to this day following two families up the Communion aisle that had just an hour earlier stolen our mailbox.
Okay, that makes sense, too.