Barbara over at SFO mom, has a great post on welcoming our visitors to Mass on Christmas. I felt a bit put out last year, when I came as early as possible to Easter Sunday Mass, and ended up standing in the vestibule anyway. I swallowed my pride, however, because that's what it is, and tried to rejoice in the extra company.
By the end of Mass, my attitude had been transformed by the Eucharist into a truly charitable one. Remember what Our Lord said about there being more rejoicing in Heaven for the return of the 100th lost sheep than for the 99 already in the fold, and don't be the Prodigal Son's cranky older brother, like I was!
A Catholic Matriarch in My Domestic Church AKA Catholic Mom has some worthwhile comments on this topic as well.