Rabbi Eliezer said ... do teshuvah (repentance) one day before your death (Ethics of the Fathers 2:15).
Rabbi Eliezer's disciples asked him, "How can we know on what day we will die?" He answered, "That is precisely the point. Since we do not know when we will die, we should live every day as though it were our last" (Shabbos 153a).
While Judaism is life oriented, and we all pray to live one hundred and twenty years, the fact is that life does come to an end, and sometimes unexpectedly so. If we were to think, "How would I like to spend my last day on earth?" and live each day as though it were that last, we would undoubtedly establish a different set of values.
If we knew that we had only twenty-four hours of life left, we certainly would not idle away these precious moments.We would not go to a movie that day. Rather, we would wish to spend every moment with the people we love, telling them how much we love them and apologizing for any possible offense done to them. We would do the same with our friends, both giving and asking for forgiveness. We might spend some time in sincere and dedicated prayer, not mumbling a word.
What a day that would be!