A few Sundays ago, I was tired. Really tired. Normally it wouldn’t be a big deal. After all, Sunday is a good day to be tired, isn’t it? It’s a "day of rest." But I had made a crucial mistake for a tired girl.

I had delayed going to Mass. I frequently attend the Sunday evening Mass here at the Cathedral in Denver. The archbishop presides and it’s always very beautiful. But when the afternoon sleepies hit me, I always regret not having gone in the morning. I desperately wanted to crawl into bed and stay there.

There had to be a way. A brief, early afternoon Mass somewhere in town? None. A dispensation? "Father, I’m really tired. Could I skip Mass today?" Highly doubtful.

So I went. It turned out fine. I caught a second wind, participated nicely, and even went out with friends after it was over.

But the whole episode got me thinking. I constantly run into people — people who consider themselves "good Catholics" — who would see fatigue as a perfectly valid reason to skip Mass. In fact, they don’t seem to have much of a problem with skipping Mass for a wide variety of reasons — skiing, travel, football, even sleeping. As long as they go "fairly regularly" they figure they’re in the clear.

They’re not.

According to the Catechism of the Catholic Church, "On Sundays and other holy days of obligation the faithful are bound to participate in the Mass." (CCC 2180) The Catechism goes on to say, "Those who deliberately fail in this obligation commit a grave sin." (CCC 2181)

I’ve been thinking a lot about this lately. Why is this such a serious matter? Why is the rule so inflexible? Does it really have to be Sunday? If we’re busy on Sunday, can’t we just move our own personal Sabbath, and attend Mass on Tuesday? We’re still going to Mass, aren’t we?

The way I see it, the answer lies not just in the third commandment ("Thou shalt keep holy the Sabbath.") but also in the first commandment.

The first commandment says "I am the Lord, thy God. Thou shalt not have false gods before me." Of course, we all think of "false gods" as Athena and Zeus and those little melted-earring calves the ancient Israelites worshipped whenever they thought Yahweh wasn’t looking. But we have our own "false gods" in 21st century America. The pursuit of wealth or power or pleasure can become a god. A hobby can become a god. A relationship can become a god. There’s nothing necessarily wrong with a hobby, or a relationship, or even the pursuit of wealth, power or pleasure, provided it is licit and pursued ethically. But when it comes before God, it becomes a problem

To me, the big question was always "How do I know it’s coming before God?" Where is the line? Should I always choose God over anything else? If I’m engaged in this pursuit and there’s a daily Mass going on somewhere, shouldn’t I be at the daily Mass instead?

Obviously, that kind of thinking could drive a person crazy. But God gave us a bit of a "litmus test" — the Sabbath.

The Sabbath is our opportunity to "put God first." He has specifically requested that we give that day to Him. If we move the Sabbath around, if we skip Mass whenever we have something we consider "more important" to do, we’re putting that "more important" thing before God. We’re fitting Him in around the rest of our lives. God wants us to build our lives the other way around. He wants us to put Him first, and to fit everything else in around Him. Sunday is our opportunity to do that. It’s where the "rubber meets the road" — where we have to decide what’s really important to us.

What does He ask us to do on Sunday? He asks us to worship Him in the holy sacrifice of the Mass, to hear His word, to receive His sacred Body and Blood. It only takes about an hour. And we have a ridiculously wide variety of options through which to fulfill His request. Masses are available in virtually every town in the civilized world. There are morning Masses, afternoon Masses, evening Masses. You can even go on Saturday evening and leave your entire Sunday free.

Think about it for a minute. Where does your life come from — your family, your loved ones, your career, your hobbies, your health, the ability to breathe in and out? It all comes from God. Without Him you would have none of it. He gave it all to you because He loves you — immensely and tenderly and completely.

And you can show Him your gratitude by making the Mass a non-negotiable part of your Sunday.