The passage, in the Loeb translation:
"I avail myself of this privilege, and every day I plead my cause before the bar of self. When the light has been removed from sight, and my wife, long aware of my habit, has become silent, I scan the whole of my day and retrace all my deeds and words. I conceal nothing from myself, I omit nothing."
Three details in that sentence do most of the work.
"When the light has been removed." It has a fixed slot, at the end of the day, in the dark, in bed. Not whenever he felt reflective.
"My wife, long aware of my habit." It was routine enough that the people around him had adjusted to it. This is a habit, not a mood.
"I conceal nothing from myself, I omit nothing." The value is entirely in the honesty. A review where you quietly skip the embarrassing part of the day is not a shorter review, it is a different exercise.