Sefer Tiferes Shmuel says that the Torah is teaching us that a person must put forth the efforts to learn Torah with enthusiasm while he is alive in this world.
One should never push off learning and say that he will do it “when he has time”. He should value every moment that he Is alive and has the ability to learn because once a person passes on the next world, there is nothing he can do to come back for even one day. He can never get back any of the time he wasted while he was alive that could have been spent learning.
Pirkei D’Rebbe Eliezer (Perek 43) relates that on the same day that Reish Lakish was nifter, two of his former comrades that he knew from the time in his life when he was a thief, before he went on to abandon that lifestyle and become a great talmid chochom, also died. The two thieves saw the great honor that was given to Reish Lakish in Gan Eden, while they were pushed around from place to place. They were confused and pained and asked: How is he different than us? Wasn’t he just like us?
They were answered: He separated from you and went to learn Torah and do mitzvos. Therefore, he deserves to be greatly rewarded.
The thieves then said, “Let us return to earth. This time, we will study the Torah!” They were told, “It is too late. You should have done teshuva when you were still alive.”
Thus, the pasuk is saying: “This is the Torah.” A person should immerse himself in Torah and teshuva. Why? Because “a man dies in a tent.” He should think about the day that he will die and imagine how that day will look. He should think about how he will wish he could do more mitzvos and learn more Torah. But it will be too late. If he does not learn Torah and do mitzvos now, he will greatly regret it later.
The Tiferes Shmuel uses this idea to explain the Mishnah (2:15) that says that a person should do teshuva “one day before he dies.” The intent of the Mishnah is that a person should always imagine that today is his last day on earth. He should think that this is his only chance to do teshuva and save himself before he moves on to the judgment of the World of Truth, where he will be judged regarding his Torah, tefillah, and behavior towards his fellow man.
Every moment should be precious and valuable to him because once this moment is gone, it can never be reclaimed. This is how a person should feel every day. He should always remember that this particular day must be used properly because it will never come back.
Sefer Toras Chaim relates that Rav Chaim of Brisk zt”l once explained this pasuk in this way and added: Imagine if it was decreed in Shomayim that all of the people who have already died would be given permission to come back to earth for one hour and to use that hour to do anything they want. Once all of the living people hear about this, they certainly will come running to see their deceased loved ones. They will run over to their relatives and ask them how they are doing in the next world.
However, the niftarim will have no time for such things. As soon as the hour arrives and their graves open to let them out, they will run to the bais medrash to learn as much as they can. They won’t waste a moment to say hello to their children and grandchildren. They won’t be interested in anything besides learning Torah.
Thus, when Chazal say that Torah only lasts if a person kills himself over it, the intention is that a person must learn Torah with the same feeling as those imaginary people who rose from the grave for an hour. If a person learns with that type of devotion, he will become great in Torah.