A businessman must periodically take inventory, balance his accounts, and determine his financial standing. Regular accounting procedures keep a business running smoothly and are a pillar of successful commerce.
However, most of his time is spent engaged in commercial activity. He pauses only to evaluate a particular transaction, to ascertain if it will be profitable, and to determine the best approach. The examination of the overall status of his business is conducted far less frequently, usually only once a year, for were it to be done every day, there would be no time to conduct any actual transactions.
We should follow the same procedures in our service to G-d, which is our "business." Most of the time - our "business year" - we deal in the "commodities" of Torah and mitzvos. Only the month of Elul, which precedes Rosh HaShanah and Yom Kippur, is the time for a "general financial review" - when we concentrate on introspection, stocktaking and spiritual accounting.
For the rest of the year, we should pause only briefly for specific, short-range assessments. For example, upon reciting the Shema each evening before retiring, we sum up the credits and debits, the achievements and deficiencies of that day; before Shabbos, we examine the accounts of the previous week; and before Rosh Chodesh (the beginning of a new month), we balance the account for the preceding month. Then, in the last month of the year, we make a comprehensive analysis of the entire year.
Some people believe that to proceed with Torah and mitzvos, they must know exactly where they stand at every moment and constantly reexamine whether they are proper candidates for spiritual service, with the accompanying detailed introspection. In reality, this approach is merely a ploy of the yetzer hara to deflect a person from appropriate action by involving him in obsessive self-analysis. He can instead proceed on his course with confidence, leaving aside this activity until its proper time.
One may ask: "Why shouldn't a person make a general accounting each day? After all, isn't a reckoning a positive thing?" He even brings proof from Tanya (ch. 29; Iggeres HaTeshuvah, ch. 11): "My shortcomings must always be before me." We then inform this person: this is a ploy of the yetzer hara. If he would constantly be taking stock of his behavior, the majority of his time would be spent on this purpose and he would lose all his time [and become depressed - which would defeat the purpose]. Subsequently, he would not [have time to] study Torah and perform mitzvos, etc.
As was related by the Rebbe Rashab: "Once, someone was found crying on Simchas Torah. He did not cry when reciting Al Cheit on Yom Kippur, so he was making up for it two weeks later. However, that was not the proper time." "G-d made man straight." For everything there is a designated time, and for stocktaking, the proper time is the month of Elul.
Likkutei Sichos, vol. 2, p. 629; vol. 9, p. 303