Marcus Aurelius supplies this quote

Love the little trade which thou hast learned, and be content therewith

Which I like for various reasons, so I just copied it from some page of Aurelius quotes, which listed the source as Meditations IV. 31..

Now I always like to see quotes in context if possible, so I tried to find it in the gutenberg text.

But then, Gutenberg says it’s actually 4:26, translated differently:
(by Florence Etienne Meric Casaubon, 1907)
http://www.gutenberg.org/dirs/etext01/medma10.txt

What art and profession soever thou hast learned,
endeavour to affect it, and comfort thyself in it;
and pass the remainder of thy life as one who from his whole heart
commits himself and whatsoever belongs unto him, unto the gods:
and as for men, carry not thyself either tyrannically or servilely
towards any.

Hey, that sounds different in meaning! “comfort thyself in it” is not the same as “be content with it”. What the?

Bartleby, where I found the original quote, has the full text, but here the 4.31 becomes:
(Translated by George Long, who died in 1879)
http://www.bartleby.com/2/3/4.html

Love the art, poor as it may be, which thou hast learned, and be content with it; and pass through the rest of life like one who has intrusted to the gods with his whole soul all that he has, making thyself neither the tyrant nor the slave of any man.

That certainly seems the closest, and may well be the actual origin of the popular saying, just simplified a bit for the books of quotes where is it found.

It seems to me the original greek is actually 4:30

http://zipper.paco.net/~yury/LL/aurel.html.utf8

Τὸ τεχνίον ὃ ἔμαθες φίλει, τούτῳ προσαναπαύου· τὸ δὲ ὑπόλοιπον τοῦ βίου διέξελθε ὡς θεοῖς μὲν ἐπιτετροφὼς τὰ σεαυτοῦ πάντα ἐξ ὅλης τῆς ψυχῆς, ἀνθρώπων δὲ μηδενὸς μήτε τύραννον μήτε δοῦλον σεαυτὸν καθιστάς.

Which is all Greek to me.

Now, I’d looked at the new (2002) translation by Hicks, and I found the language dull and uninspired. Looking up this phrase we have:

Cherish your gifts, however humble, and take pleasure in them. Spend the rest of your days looking only to the gods from whome come every good gift and seeing no man as either master or slave

“Cherish your gifts”? Pap! “your gifts” is not the same as “the art, poor as it may be, which thou has learned”. Danggit, now I’ve got to translate the original Greek to see what he really said. Are the Hicks dumbing it down, or did the older translators spice it up?

Another modern translation, Gregory Hays, 2002:

Love the discipline you know and let it support you. Entrust everything willingly to the gods, and then make your way through life – no one’s master and no one’s slave

Better. “Discipline” is better, but still so distinct in meaning from the old timers.

Back to the “original”

Love the little trade which thou hast learned, and be content therewith

This is listed as the quote in lists of quotes and aphorisms. Indeed the first use I find is in 1906, in a book “Familiar Quotations” by John Bartlett.

Rather oddly it is also attributed to “Mabel Ashburton” in the 2005 book of quotes, “The White Wallet”. “Mabel Ashburton” does not appear on the internet, but is probably “Mabel Edith Baring” (nee Hood), Lady Ashburton, which is confusing until we find The White Wallet was actually written by Viscountess Pamela Grey of Fallodon, in 1912, collecting and publishing quotes being an acceptable occupation for a gentlewoman. Probably Mabel stole it from Bartlett, and offered it to Pamela as her own.
http://www.thepeerage.com/p8064.htm#i80632

We also have a latin version, by J. M. Schulz, 1802
http://www.slu.edu/colleges/AS/languages/classical/latin/tchmat/pedagogy/latinitas/ma/ma4.htm

Artem, quam didicisti, diligito et in ea acquiesceto: quod autem vitae super est, id ita exigito, ut qui Deo omnia ex toto animo commiseris, neque ullius hominis aut dominum aut servum te praebeto.

Transliterated very badly:

Art, how learnt, esteem and in also (?accquire?), that also life/career beyond is
http://www.archives.nd.edu/cgi-bin/words.exe?Artem%2C+quam+didicisti%2C+diligito+et+in+ea+acquiesceto%3A+quod+autem+vitae+super+est%2C