We can thank Pope Saint Pius X for allowing us to receive Communion as much as twice a day, and even a third time in the form of Viaticum. This is reflected in the Code of Canon Law:
Can. 917 A person who has already received the Most Holy Eucharist can receive it a second time on the same day only within the eucharistic celebration in which the person participates, without prejudice to the prescript of ⇒ can. 921, §2.
Can. 921 §1. The Christian faithful who are in danger of death from any cause are to be nourished by holy communion in the form of Viaticum.
§2. Even if they have been nourished by holy communion on the same day, however, those in danger of death are strongly urged to receive communion again.
§3. While the danger of death lasts, it is recommended that holy communion be administered often, but on separate days.
Aside from the number of times a day one may received Our Lord in the Blessed Sacrament, there are a number of other impediments to receiving Communion. Of course, only Catholics who have received their First Communion, and have no grave sins that have not been brought to confession may receive Communion. Most know this, but many don’t realize that such grave sins that would be an impediment would be the use of contraception and missing a Holy Day of Obligation without a just reason. While Holy Days of Obligation may vary form place to place, all Sundays are Holy Days of Obligation. Thus, C&E Catholics cannot receive Communion on the two days of the year they come to Mass unless they go to Confession; and, a Confession is not valid unless you actually attempt not to commit the sins confessed. (If you fail in this attempt, don’t worry, just go to Confession again.)
There may be other reasons not to receive Communion, such as failing to observe the hour fast before receiving Communion (this is only the minimum, you can fast for longer if you choose) or if receiving Communion would require committing a liturgical abuse.
When you assist at a Eucharistic Liturgy at which you do not receive Communion, you can make a Spiritual Communion. In fact, you can do this often, even more than three times a day. Perhaps a good habit would be to make a Spiritual Communion every time you pass a church with the Blessed Sacrament inside, as would on days in which you cannot assist at a Eucharistic Liturgy.
You may use whatever words you wish to make a Spiritual Communion; however, the following one composed by St. Alphonsus Liguori is very popular:
My Jesus, I believe that You are truly present in the Holy Eucharist.Source of prayer: http://stmichael.caedm.ca/SpiritualCommunion.pdf
I love You above all things, and I desire to receive You into my soul.
Since I cannot at this moment receive You sacramentally,
come at least spiritually into my heart.
I embrace You as if You were already there,
and unite myself wholly to You.
Never permit me to be separated from You.
This is another translation:
I believe that You are Really Present in the Blessed Sacrament
and I long to receive You into my soul.
Since I cannot now receive You sacramentally,
come at least spiritually into my heart...
I embrace You, as One Who has already come
and I unite myself entirely to You.
Never permit me to be separated from You.
The reason I use the term Eucharistic Liturgy is because the term Mass is technically only correct for the Eucharistic Liturgy of the Latin Rite (i.e. The Roman Catholic Church). The Eucharistic Liturgies in the other rites, such as the Byzantine Rite, of which the Ukrainian Catholic Church is but one jurisdiction, usually use the term Divine Liturgy (e.g. The Divine Liturgy of Saint John Chrysostom). Roman Catholics can receive Communion at a Divine Liturgy of another rite if that Church is in union with Rome; and, under special circumstances, even in a Church that, while united in the Sacraments with Rome, is not in complete union with Rome (i.e. The Orthodox Churches).
Can. 844 §1. Catholic ministers administer the sacraments licitly to Catholic members of the Christian faithful alone, who likewise receive them licitly from Catholic ministers alone, without prejudice to the prescripts of §§2, 3, and 4 of this canon, and ⇒ can. 861, §2.
§2. Whenever necessity requires it or true spiritual advantage suggests it, and provided that danger of error or of indifferentism is avoided, the Christian faithful for whom it is physically or morally impossible to approach a Catholic minister are permitted to receive the sacraments of penance, Eucharist, and anointing of the sick from non-Catholic ministers in whose Churches these sacraments are valid.
§3. Catholic ministers administer the sacraments of penance, Eucharist, and anointing of the sick licitly to members of Eastern Churches which do not have full communion with the Catholic Church if they seek such on their own accord and are properly disposed. This is also valid for members of other Churches which in the judgment of the Apostolic See are in the same condition in regard to the sacraments as these Eastern Churches.
§4. If the danger of death is present or if, in the judgment of the diocesan bishop or conference of bishops, some other grave necessity urges it, Catholic ministers administer these same sacraments licitly also to other Christians not having full communion with the Catholic Church, who cannot approach a minister of their own community and who seek such on their own accord, provided that they manifest Catholic faith in respect to these sacraments and are properly disposed.
§5. For the cases mentioned in §§2, 3, and 4, the diocesan bishop or conference of bishops is not to issue general norms except after consultation at least with the local competent authority of the interested non-Catholic Church or community.