Remember, the Ramchal says one mitzvah (commandment) would have been enough for Adam HaRishon. How many mitzvot have you already accomplished in this world? Thousands upon thousands of mitzvot. But what does the Yetzer Hara (evil inclination) do? And he's the best at this. He takes a mitzvah, shoves it down, and minimizes it as if it's nothing, as if it's not a big deal. So you did Birkat Hamazon—whoop-de-doo, big deal.
But, you know, the Brisker Rav says it like this: If someone comes over to you—let's say you're about to say Birkat Hamazon—and tells you, “This is your last day on earth. This is your last hour. This is your last mitzvah, and you're the only Jew left in the world to accomplish this mitzvah,” would a person feel differently when he starts doing that mitzvah? Absolutely. Last day, last hour, last mitzvah—and you're the only Jew to do this mitzvah, Birkat Hamazon.
If a person would think like that, it would be a game changer for his outlook and for the value he gives to the Birkat Hamazon mitzvah. But what happens? We tell ourselves, “It's not the last day on earth. We did many mitzvot. We're going to do many mitzvot. There are many. There are many Jews in the world. What's the big deal in other Birkat Hamazon?” Then we minimize the mitzvah. But that's a mistake, because the truth is, you don't know when your last mitzvah is. But even more than that, every one mitzvah you're about to do, and you're going to have a long life. But it doesn't mean the next mitzvah you're going to do is not a big deal. Every mitzvah is a major deal.
You value the mitzvot you do; you realize how much you accomplished. You realize how much you accomplished, and you'll be b'simcha. That person will be happy. You're going to serve Hashem with happiness because you accomplished a lot, and you really did accomplish a lot. And at the same time, you're also going to realize how much you could accomplish in this world. Every mitzvah in this world.