“Respice post te! Hominem te esse memento! Memento mori!”
— In ancient Rome, the words are believed to have been used on the occasions when a Roman general was parading through the streets during a victory triumph. Standing behind the victorious general was his slave, who was tasked to remind the general that, though his highness was at his peak today, tomorrow he could fall or, more likely, be brought down. The servant conveyed this by telling the general that he should remember, “Memento mori.” It is further possible that the servant said instead, “Respice post te! Hominem te esse memento! Memento mori!”: “Look behind you! Remember that you are but a man! Remember that you’ll die!”, as noted by Tertullian in his Apologeticus.
Source:
https://quotevadis.tumblr.com/post/9545467030/memento-mori