Musar su Ecclesiaste 9:9

And this is the intent of the verse (Koheleth 9:9): "See life with the woman that you love all the days of the life of your vanity, for that is your portion in life." "the woman that you love" alludes to Torah ["that you love" — for "one learns Torah only in the place (i.e., the subject) that his heart desires" (Avodah Zarah 19a)] And Scripture has exhorted us not to miss one day of Torah, for that is our portion in life. "your vanity" alludes to one who gives thought to himself to guard all of the days that he lives on the earth, not to waste one day, realizing that this world is a world of vanity, and that he has been sent here only to do the embassy of the Master of the world, to attain his portion in the Torah and in the fulfillment of mitzvoth in order to shine in the light of life in the world to come. About such a man we can hope that he will guard his days, that not one day will go to waste. In sum, just as the men of great wealth, who possess notes of great value, guard them vigilantly, each one of them representing a portion of their wealth, so, exactly, must the man of heart guard his days and hours, each of them being his portion in life. The maxim of the sage is well known: "There is no loss like the loss of time." For if a man loses a dinar from his pocket, he can hope to find it or that the Holy One Blessed be He will grant him a different one instead. But if a certain hour goes to waste, he will never find it again. And he will be made to face this when he comes for his accounting in time to come and they set out before him how he had spent his days and hours, as it is written (Psalms 50:21): "I shall reprove you; I shall set it out before your eyes." Chazal have said: "They illumine all of his deeds before him. Then he will bemoan himself over his conduct, but who will be able to help him then?" Happy is he who bethinks himself of all this while he yet lives!

And, in truth, "And if not now" implies "every hour and every day." One must think "If not now" — that the Holy One Blessed be He determines for a man every day what he is to attain of the Torah of the L-rd and His service. As to the yetzer's enticing him that tomorrow he can make up for today, this is an error. For tomorrow is an obligation in itself, and he will not be able to make up the time that he lacks now. And only from day to evening [of the same day] do we find in Chazal: "One may borrow [of his time] in the daytime and make it up [in Torah study] at night." And this is the intent of (Devarim 4:9): "And lest they depart from your heart all the days of your life." And thus, (Koheleth 9:9): "And see life… all the days of your vanity" — that is, that not one day go lost. And thus, (Rambam, Hilchoth Talmud Torah 1:10): The verse "And lest they depart from your heart all the days of your life" implies that one may not be idle in the Torah of the L-rd for even one day — until his last day. And this is intimated in the verse (Mishlei 3:28): "Do not say to your friend: 'Go and return, and tomorrow I will give you,' if you have it with you [today]." "your friend" is the good yetzer, a man's true friend, who counsels him as to what will be good for him forever.