Take heed not to be transformed into a Caesar, not to be dipped in the purple dye; for it does happen.

[Ὅρα μὴ ἀποκαισαρωθῇς, μὴ βαφῇς: γίνεται γάρ.]

Marcus Aurelius (AD 121-180) Roman emperor (161-180), Stoic philosopher
Meditations [To Himself; Τὰ εἰς ἑαυτόν], Book 6, ch. 30 (6.30.1) (AD 161-180) [tr. Farquharson (1944)]
    (Source)

Advising himself on the dangers of becoming emperor. Marcus coined a new Greek verb here (ἀποκαισαρόομαι), "to become like Caesar" (more broadly, "to assume the monarchy").

(Source (Greek)). Alternate translations:

Take heed, lest of a philosopher thou become a mere Caesar in time, and receive a new tincture from the court. For it may happen if thou dost not take heed.
[tr. Casaubon (1634), 6.27]

Have a care you han't too much of an Emperour in you, and that you don't fall into the liberties and Pride of your Predecessors. These Humours are easily learn'd, therefore guard against the Infection.
[tr. Collier (1701)]

Take care you don’t degenerate into the manners of the Cesars, or be tinctured by them.
[tr. Hutcheson/Moor (1742)]

Beware, when you take the title of Cæsar, that you do not insensibly assume too much of the Emperor; nor be infected with the haughty manners of some of your predecessors; for there is a possibility of such an event.
[tr. Graves (1792), 6.27]

Take care that thou art not made into a Caesar, that thou art not dyed with this dye; for such things happen.
[tr. Long (1862)]

Have care that you have not too much of a Cæsar in you, and that you are not dyed with that dye. This is easily learned, therefore guard against the infection.
[tr. Collier/Zimmern (1887)]

See that you be not be-Cæsared, steeped in that dye, as too often happens.
[tr. Rendall (1898)]

See to it that you fall not into Caesarism: avoid that stain, for it may come to you.
[tr. Hutcheson/Chrystal (1902)]

See thou be not Caesarified, nor take that dye, for there is the possibility.
[tr. Haines (Loeb) (1916)]

Be careful not to affect the monarch too much, or to be too deeply dyed with the purple; for this can well happen.
[tr. Staniforth (1964)]

Take care that you are not turned into a Caesar, that you are not stained with the purple; for such things do come about.
[tr. Hard (1997 ed.; 2011 ed.)]

To escape imperialization -- that indelible stain. It happens.
[tr. Hays (2003)]

Take care not to be Caesarified, or dyed in purple: it happens.
[tr. Hammond (2006)]

Take care you are not turned into a Caesar, or stained with the purple; these things do happen.
[tr. Gill (2013)]

Beware of being Caesarified, be not stained by desire for power.
[ed. Taplin (2016)]