On Rosh Hashana: For All My Life

The Talmud in Kiddushin (40b) has a fascinating passage describing the merits process, which is quite applicable to this time of year.
“Our Rabbis taught: A person should always regard himself as though he were half guilty and half meritorious: if he performs one mitzvah, happy is he for weighting himself down in the scale of merit. If he commits one transgression, woe to him for weighting himself down in the scale of guilt. It is said, ‘But one sinner destroys much good’ (Kohelet 9). In other words, on account of a single sin which he commits much good is lost to him.
“R. Eleazar son of R. Shimon said: Since the world is judged by its majority, and an individual is also judged by his majority [of deeds, good or bad], if he performs one good deed, happy is he for turning the scale both for himself and for the whole world on the side of merit. But if he commits one transgression, woe to him for weighting himself and the whole world in the scale of guilt, for it is said: ‘but one sinner, etc.’ — on account of the single sin which this man commits he and the whole world lose much good.
“R. Shimon Bar Yohai said: Even if he is perfectly righteous all his life but rebels at the end, he destroys his former [good deeds], for it is said: The righteousness of the righteous shall not deliver him in the day of his transgression (Yechezkel 33). And even if one is completely wicked all his life but repents at the end, he is not reproached with his wickedness, for it is said, ‘And as for the wickedness of the wicked, he shall not fall thereby in the day that he turns from his wickedness’ (ibid).
“Yet let it be regarded as half transgressions and half meritorious deeds! — Said Resh Lakish: It means that he regretted his former deeds.”
The first part of the passage describes the scale we all envision – where our positive deeds and fulfilled mitzvot sit on one weight counter, being weighed against our bad deeds, violations of sin and transgressed negative commandments. This balance act of merits versus demerits is easy for us to understand.