One moment spent engaged in teshuvah (repentance) or ma'asim tovim, good deeds in this world, is greater than the entire lifetime in the world to come. What we're basically saying here is that there's one difference between this world and the next world. In this world, a person has the ability to grow, achieve, and be involved in teshuvah and ma'asim tovim. Because of that, this world offers a person the opportunity to become something greater. In contrast, in olam haba (world to come), once a person passes away and goes to olam haba, that's the end of the line for him. He has no ability to grow. It doesn't offer that person the ability to accomplish something differently. A person has his ticket stamped once he passes away and goes to olam haba, and he has that position wherever he is for eternity. In contrast, in this world, a person can build himself up with one little mitzvah (commandment).
That's the famous story of the Vilna Gaon, who was crying on his deathbed. He was holding a pair of tzitzit (ritual fringes), and he was crying. He said, “I have the ability to achieve great heights when I put on this pair of tzitzit, and I'm about to leave that. When I go to olam haba, even though I know I'm going to olam haba, I don't have the ability to grow anymore.” So he mourned the fact that he was leaving behind the ability to grow and was sort of clocking out at that level. Even though it was a great level, it's the end of the line in terms of growth for a person once he leaves this world. So we say that this world, in a certain sense, is greater than the next world, because a person has the ability to continue, grow, and accomplish.
One moment of enjoyment in the world to come is better than an entire lifetime of pleasure. What we're saying here is that, as we said in the last Mishnah, olam haba is greater than this world on two levels: a qualitative level and a quantitative level. On a qualitative level, the enjoyments a person has in this world are simply desires that he may have. They're limited in what they actually achieve. On a qualitative level, it's just a person possibly fulfilling a biological need or enjoying something that's really nonsense at the end of the day, when you really think about it. So, on a qualitative level, olam haba is a spiritual bliss that a person experiences with Hashem, indescribable in human terms. So qualitatively, olam haba, of course, is much better.
And then, even quantitatively, in terms of how much enjoyment a person has in this world, a person's enjoyment is always mixed in with troubles, stresses, and anxieties that are always part of life, and the enjoyment ends at some point in time. It could be a 10-minute pleasure; it could be a year of pleasure. But at a certain point, even if it's a full life—95 years of pleasure—it all comes to an end, as opposed to the total bliss that olam haba offers an individual.