The short answer
The Tong Shu, the Chinese almanac, is a daily reading of the calendar's energy. For each day it names the ruling 'day officer', the animal it clashes with, the auspicious and inauspicious stars, and what the day favours or forbids.
The heart of it
Twelve day officers rotate in a fixed order — Establish, Remove, Full, Balance, Stable, Hold, Break, Danger, Success, Collect, Open, Close. Each favours a kind of act and warns against its opposite; 'Open' and 'Success' days suit beginnings, 'Break' and 'Danger' days do not.
Why it is worth your attention
Checking the day's officer before the inbox is an old strategist's habit: place demanding work on strong days and routine admin on weak ones, and let the calendar carry some of the load.
Try it yourself: The Chinese Almanac (Tong Shu) is free on FengMaster, computed to the letter.