Tai Yin is the moon, and it pairs exactly with the sun: the sun points outward, public, given to everyone; Tai Yin points inward, private, given to a few. That isn't a difference in strength but in the reach of the light. Moonlight doesn't dazzle, which is why it gets into places the sun can't.
It shows up in you like this: your private self and your public self differ considerably, and the private one is the real one; your read on detail and atmosphere is accurate before anything is said; and your energy is fuller at night or in quiet.
Running well, Tai Yin is whoever does the fine work: planning, accumulating, caring, running a thing — all slow work, and whether it's done well is only visible up close. Blocked, inwardness becomes retreat: keeping the idea inside and then resenting that nobody saw it, or turning the whole sensitivity inward until you can't let yourself off anything. The tradition says Tai Yin governs wealth rather than rank, and practically that means your returns come from accumulation rather than from contest — so there's no need to check yourself against anyone else's tempo.