辛 is the yin face of metal: metal already worked — jewellery, the needle, the fine blade. Its difference from 庚 is precision rather than force: 庚 splits, 辛 cuts exactly. So 辛's sensitivity isn't an emotional matter; the work needs that resolution.
You'll recognise it here: you see gaps others don't, and a millimetre off is glaring; you care about how you present to a nearly severe degree, which isn't only vanity — you know detail speaks; and coarse things make you physically uncomfortable, coarse treatment included.
Running well, 辛 takes quality where others can't: a layer of difference most people can't name, which nonetheless sells, gets remembered, and lasts. Blocked, that accurate ruler turns on you and on the people near you — permanently a little short, with another little behind it. The tradition says 辛 is spoiled by burial and by heavy blows: it needs to be seen, and it needs to be handled gently. So its practical lesson is keeping the ruler on the work, and allowing people to be rough — yourself included.
