Why is it a Mortal Sin? Skipping Mass and Communion without Confession

Why is skipping mass a mortal sin? And when we do go to mass, why
do we need to receive communion in a state of grace? It’s tempting
to believe we can love God in whatever way suits us, but that’s not
how love works. The way we express our love for God is through
obedience and worship. Fr. Mike speaks a harsh truth when he says,
“If you love God on your own terms, you don’t love God, you love
yourself.” In the first of two explanations, Fr. Mike explains that
going to Mass on Sunday is our weekly chance to prove our love for
God. Fr. Mike’s second lesson in this video addresses the issue of
receiving Communion in the state of mortal sin, which follows the
logic of the first lesson above. Communion with God is only
possible once we have been reconciled with God and his Church. Both
Christ and St. Paul make this clear: “So if you are offering your
gift at the altar, and there remember that your brother has
something against you, leave your gift there before the altar and
go; first be reconciled to your brother, and then come and offer
your gift” (Matthew 5:23-24). “Whoever, therefore, eats the bread
or drinks the cup of the Lord in an unworthy manner will be guilty
of profaning the body and blood of the Lord.” (1 Corinthians
11:27). Fr. Mike briefly addresses what sin is, and directs his
viewers to this previous episode of his wherein he addresses the
topic more thoroughly: What is Sin?