Someone at Mass today did not come forward to receive communion. How do you feel when you hear that? Sad? Confused? Happy? What thoughts go through your mind when you see something like that? Have you ever seen something like that (except for non-Catholics)? What would you say (if anything) to the person after Mass if you saw that? All of these questions are important for you to ask yourself, because they will reveal much about your understanding of Holy Communion.
The first question that many ask in this regard is, "isn't that wrong? aren't you supposed to receive communion every time you go to Mass?" I would really like to know where this idea came from. Somewhere along the line the faithful were encouraged to receive communion at Mass regardless of whether they were in a state of grace or not (which is an insidious error). The faithful are forbidden from receiving Holy Communion if they have unconfessed (and therefore unforgiven) grave sin in their lives. What have you been taught in this regard?
Did you know that many of the Saints of years ago received communion only on rare occasions? This was not because they were lazy or disrespectful toward Jesus (just the opposite!); it was because they wanted to be sure that they were "rightly disposed" before they partook of the Sacrament. There was something else going on here as well; they realized that the sacrifice of the Mass was more important than their personal reception. In fact, only the celebrant is actually required to receive at the Mass, for when he receives he is completing the sacrifice itself (and the consecration is not considered complete until the priest has received both body and blood).
There certainly might be various reasons why someone would not receive communion at Mass; both good and bad. Maybe someone does not believe in the Real Presence of Christ in the sacrament and wants to avoid "superstitions" (someone once told me this was his belief). Maybe someone has just returned to the Church after being away for years and wants to go to confession first (a great reason!). Finally, maybe someone is not Catholic and knows that he is not supposed to receive the sacrament (regardless of what some German Bishops would say). Other than something similar to these three reasons, the primary reason why a Catholic would abstain from the reception of communion in the Mass is because he knows that he is only supposed to receive communion in a state of grace and that to receive otherwise is another grave sin on top of what is already there.
Technically speaking, since none of the faithful are required to receive communion more than once a year (yes, you read that right), there is nothing wrong with attending Mass faithfully on Sundays and Holy Days of Obligation and not receive for quite a while. Because the Sacrament provides grace for the life of faithfulness, we would not want someone to err so far in this direction that he were avoiding the Sacrament. There is still grace to be received in the body and blood of Christ, but it is better to be working on your sins and abstain than to ignore your spiritual condition and come to communion in a state of grave sin.
It would be better to take those few minutes before the Mass to do a healthy self-examination and ask yourself "am I rightly prepared to receive communion today?" (how many times have you done that?) than to assume that you are required to receive communion every time. Furthermore, in this context, it is obligatory for the rest of the faithful to look with humility upon someone who stays in the pew during the distribution of communion (there is no criticism for someone who respects the sacrament so much that he chooses to wait to receive it).
So when someone does not receive communion at Mass, and is doing it because he or she is concerned with being right before God, it is commendable -- did you read that? Commendable! It is a good and godly thing: it says "I'm not taking this for granted" as well as "I am concerned that I be fully and rightly prepared to come to the rail." In fact, were everyone in a single parish to acknowledge this important truth, then less and less people would come to communion every week. In addition, more and more people may very well spend more time working on their spiritual state and less time trying to look perfect in front of everyone else.