This is a proverb my father, grandpa and grandma (pretty much all of my family members, very often) would use when seeing a person with a profession apply zero to none of their skills for themselves.
I am a Persian descendant, and sayingsayings like thisthese are countless.
The famous one and my favorite of is: This too shall pass!
The story comes from an ancient potter who made very beautiful potteries, mostly used for drinking water.
Back themthen drinking jars made out of clay would keep the water colder than any other jars. theThe clay would help cool down the water inside, when was wrapped bywith a moist cloth around it.
The potter himself had a broken one that was at the corner of his store and would use that. heHe was very busy making pottery frfor others, and his would do the job anyways, so why bother.
However in this society this has gone, in some cases to the extreme. For example, a psychologist or a life coach who'swhose life is in a total mess, but has helped hundreds to reach phenomenal results.