There is an idea out there that missing Mass is not that big of a deal, but in actuality, missing Mass without sufficient reason is "grave matter," that is, if it is done with full knowledge and consent of the will, it would need to be confessed before receiving the Lord in the Eucharist. But you may ask, "Is it really that big of a deal? After all, aren’t we supposed to worship in 'spirit and truth' (Jn 4:23)?" The answer is yes, we are supposed to worship in ‘spirit and truth,’ but that does not preclude Mass attendance. In context, here is the entire statement of Jesus where that phrase is included:
Jesus said to her, "Woman, believe me, the hour is coming when neither on this mountain nor in Jerusalem will you worship the Father. You worship what you do not know; we worship what we know, for salvation is from the Jews. But the hour is coming, and now is, when the true worshipers will worship the Father in spirit and truth, for such the Father seeks to worship him. God is spirit, and those who worship him must worship in spirit and truth." (John 4:21-24)
This is not a call to forego formal worship altogether, but only that centralized worship would be abrogated. Quite to the contrary, from Genesis to Revelation, a very strong emphasis has been placed on proper worship. If you read the first creation account of Genesis, the structure seems to indicate that all of creation is directed towards worship in the Sabbath. In his book, In the Beginning: A Catholic Understanding of the Story of the Creation and the Fall, then Joseph Cardinal Ratzinger says this:
Creation is designed in such a way that it is oriented towards worship. It fulfills its purpose and assumes significance when it is lived, ever new, with a view to worship. Creation exists for the sake of worship.
Further evidence of the Sabbath orientation of creation can be seen in the language of the Sabbath ordinance of Exodus:
Remember the Sabbath day, to keep it holy. Six days you shall labor, and do all your work; but the seventh day is a Sabbath to the LORD your God; in it you shall not do any work, you, or your son, or your daughter, your manservant, or your maidservant, or your cattle, or the sojourner who is within your gates; for in six days the LORD made heaven and earth, the sea, and all that is in them, and rested the seventh day; therefore the LORD blessed the Sabbath day and hallowed it. (Exodus 20:8-11)
We also know that there is a right way to worship and a wrong way to worship. This is known by the narrative concerning Cain and Abel. For whatever reason, as the Scriptures are not clear, Cain’s offering was rejected, and Abel’s was accepted. Even though we are lacking in details, we do know, that for whatever reason, God rejected the offering of Cain.
At this, an objection can be raised. “These are Old Testament references. Ritual doesn’t matter anymore.” To this I respond, “Wrong!” All Christians agree that the Last Supper was the institution of the Sacrament of the Eucharist (the Lord’s Supper). However, what escapes many is the simple fact that this was done in the context of the Passover liturgy celebrated by the Jews. To say that Jesus rejected liturgical celebration is unsupportable. What He did was change the meaning of existing liturgy. Instead of a “type” looking forward to a future event, it became a participation in the Cross. This is not to say that worship is impossible outside of the liturgy. We can pray, engage in Eucharistic adoration, go to Charismatic “praise and worship” services, and so on, but they are not the same as Mass for the simple reason that when doing these things you are not entering into the heavenly liturgy described in the Apocalypse. To do so requires a priest or bishop, acting In persona Christi, that is, “in the person of Christ” to pronounce the words of consecration and thereby bringing heaven and earth into intersection. This cannot be done outside of Mass.
My question is this: If the Mass is a sacrifice that results in the intersection of heaven and earth, if it indeed is the worship depicted in Isaiah 6: 1ff, why would anyone not hunger for this? Why would anyone wish to avoid it?