The phrase "hast one nose grindstone" is an old proverb that means to be overly focused on oneself or to be excessively self-critical. There are several other phrases and idioms that express a similar sentiment, including "nose to the grindstone," which means to work hard and persistently, and "navel-gazing," which means to be excessively self-involved. Other synonyms for being self-centered or self-absorbed include "egotistical," "narcissistic," and "self-obsessed." These types of behaviors can be counterproductive and damaging to relationships and personal growth, so it's important to be aware of them and work to overcome them.