Aphorisms
“If you wish me to weep, you yourself
Must first feel grief.”
Source: Ars Poetica, or The Epistle to the Pisones (c. 18 BC), Line 102
Original
Si vis me flere, dolendum est primum ipsi tibi.
Help us to complete the source, original and additional information
Horace 92
Roman lyric poet -65–-8 BCRelated quotes

Memoirs (trans. Machen 1894), book 1 (Venetian Years), chap. 14 http://etext.library.adelaide.edu.au/c/casanova/c33m/chapter14.html
Referenced
“Before facing you enemy, you must first face yourself.”
Source: Bleach―ブリーチ― 33 [Burīchi 33]

“To love others you must first love yourself.”
Source: Love

“The first principle is that you must not fool yourself — and you are the easiest person to fool.”
" Cargo Cult Science http://calteches.library.caltech.edu/51/2/CargoCult.htm", adapted from a 1974 Caltech commencement address; also published in Surely You're Joking, Mr. Feynman!, p. 343
Variant: The first principle is that you must not fool yourself — and you are the easiest person to fool.

translation from the Dutch original: Fons Heijnsbroek
version in original Dutch / citaat van Paul Gabriël, in Nederlands: Wees wat, weest U zelve, zoo niet gooi uw palet in ’t vuur. Vormt een school zoo ge wilt, maar het moet uit U komen, maar gij zelve mag tot geen school behooren.
In a letter of Gabriël, Brussel (14 Oct. 1879), to his student then Willem Bastiaan Tholen; in Gabriël, P.J.C, ed. Jeltes, H.F.W.; Gebroeders Binger, Amsterdam 1926; as cited in an excerpt of RKD Archive, The Hague https://rkd.nl/explore/excerpts/136
1860's + 1870's

“To weep is to make less the depth of grief.”
Source: King Henry VI, Part 3