The personality is bound to the physical body; since it is just an energetic shell, it relates to the fourth dimension (yesod).
You are right that it is not easy to assign "consciousness" to one sephirah, since one has consciousness even in the Absolute. If we analyze the experience of being (or consciousness), we can see that it is like a radiance or ray that extends from the Absolute into manifestation, beginning in an abstract, universal sense of being, and as it proceeds through the tree is becomes more "particularized" through Chesed, Geburah, and Tiphereth, where is can finally be called "human being" or "human consciousness." The sephiroth below them are not consciousness, but are the vehicles through which that consciousness perceives and understands the lower manifestations of nature (5th, 4th, and 3rd dimensions).
Regarding the reins, you found a typo! Thank you! It should read:
"Woe unto the coachman who does not know how to handle the reins."
"Do not worry; cultivate the habit of being happy." - Samael Aun Weor