Musar על ראש השנה 32:17

...Our rabbis taught (Rosh Hashanah 16b): "Three books are opened on Rosh Hashanah - one for thoroughly righteous people, one for thoroughly evil people, and one for the average people. Thoroughly righteous people are inscribed and sealed immediately for life; thoroughly evil people are inscribed and sealed immediately for death; average people remain undetermined for between Rosh Hashanah and Yom Kippur. If they merit it, they are inscribed for life; if they do not merit it, they are inscribed for death." That which the sages said of righteous people - that they are inscribed for life - or evil people - that they are inscribed for death - is not said of righteous people who have no sins or evil people who have no merits, for many righteous people die immediately, and many evil people live long lives in serenity. Also, the verse (Ecclesiastes 8) cries out "that there are righteous people whose experiences [would be fitting recompense for] the actions of evil people, and evil people whose experiences [would be fitting recompense for] the actions of righteous people." Already, Sages have said (Pirkei Avot 4) that "it is within our grasp [to understand] neither the tranquility of the wicked nor the suffering of the righteous." Rather, this is the rule: There are sins that - as determined by The Holy One, Blessed is He and His just laws - are requited for in this world, and there are some in which the law is that they will be requited for in the world to come. So also for merits - there are some of them for which the Master of Reward pays their wages in this world, and some in the world to come. When a man sins constantly and begrimes himself with iniquities and besmirches himself with sins and rolls around in his wanton violations, but also does acts of charity and good deeds - when his actions come before the Master of All, He weighs these actions against those. The righteous person who is thoroughly righteous achieves life, and similarly the evil person - whose verdict it is that he will be paid his reward in this world for his good actions - is also inscribed and sealed immediately on Rosh Hashana for life. That is to say, that he [the evil man] is awarded life, serenity, wealth, possessions, and honor.

Now according to the extent of one's habituation to this trait, so will there be diminished from him the sin of lashon hara. How much, then, must a man strengthen himself in this trait, to judge every man in the scales of merit. For on this trait or on the reverse, G-d forbid, can easily depend a man's being called a tzaddik or a rasha [wicked] forever. For it is known that a man's guilt or merit depends upon the majority of his mitzvoth or sins, as Chazal have stated in many places. If the majority [of his deeds] are mitzvoth, he is called a tzaddik; and, if sins, he is called a rasha. And Chazal have said (Rosh Hashanah 16b): "Three books are opened on the day of judgment [(that is the "great" day of judgment at the resurrection [viz. Rashi])]. The absolutely righteous are written down and sealed immediately for eternal life. The absolutely wicked [(that is, those with a majority of sins [viz. Rashi])] are written down and sealed immediately for Gehinnom." Now it is well known that in respect to a man's merits, even if they be as many as the sands [of the sea], if the Holy One Blessed be He conducts Himself with him according to the absolute measure of din [judgment], there will remain with him only a miniscule amount. For with many of them he will not have fulfilled them in all the details and aspects relevant to that mitzvah. And even those he did fulfill thus, would not have been fulfilled with the love and the fear and the joy appropriate for the doing of the mitzvah. In sum, if the Holy One Blessed be He were exacting, G-d forbid, as to the doing of His mitzvoth, most would be found blemished, and the remaining mitzvoth would not constitute a minority of a minority of his sins, and he would be called a rasha for eternity. But if the Holy One Blessed be He conducted Himself with him according to the attribute of mercy, and sought merit for him in all of his acts, his merits would remain intact. More than this, even if his deeds were counted and he were found to have a majority of sins, if the Holy One Blessed be He would conduct Himself with him according to the absolute measure of mercy, his sins would be diminished. For there would certainly be found many sins which could be attenuated because of his having committed them unwittingly, or for some other reason. In sum, if the Holy One Blessed be He wished to seek merit for a person, there would be no hindrance to His doing so, and if, as a result, some of his sins were diminished, the scale of merit would predominate and he would be called a tzaddik for eternity.

I shall elucidate this with a telling analogy: There was once a great miser who never shared his bread with the poor, and scrounged for many years with every household expense, whereby he accumulated several hundred rubles of silver. This miser was always contemplating new possibilities of saving, and he finally decided that he would begin to be sparing of the bread that he ate, and so he did. The first month he habituated himself to doing without a quarter of a litre of bread every day. By doing so, his pocket became fuller and he rejoiced greatly in this as was his wont; and he felt no frailty of heart because of this. And, in the third month, when he had become accustomed to this, he began to scrimp on another quarter of bread, until, with the passage of days, he began to feel frail of heart and went to a doctor, who said to him: "You are suffering from emaciation, and there is almost no cure for this; however, I have a certain drug, which may cure you, but it will cost you two hundred silver rubles." When the miser heard this, he fled from the doctor's house. But his condition worsened every day, and he saw that his end would be terrible, so he went again to the doctor, and begged him: "Give me that drug that you spoke about and I will give you whatever you want, for 'my soul is at the gates of death.'" The doctor replied: "I will have to know the source of your disease to know how to prepare the drug." The miser turned to him and said: "I must admit that I myself am the cause of it." And he told him the whole story. The doctor responded: Silly man, all together you have saved about four or five rubles, and you have endangered your life. And who knows for a certainty that this drug will help you! What is more, you must now spend fifty times your profit!"