“The easiest person to deceive is one’s own self.”
The Disowned (1828), Chapter xlii.
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Edward Bulwer-Lytton 31
English novelist, poet, playwright, and politician 1803–1873Related quotes

Original: Non ingannare mai una persona corretta. Una persona corretta, quando la inganni può diventare peggiore di una persona scorretta.
Source: prevale.net

“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.

Third Olynthiac http://books.google.com/books?id=n4INAAAAYAAJ&q="the+easiest+thing+in+the+world+is+self-deceit+for+every+man+believes+what+he+wishes+though+the+reality+is+often+different"&pg=PA57#v=onepage, section 19 (349 BC), as translated by Charles Rann Kennedy (1852)
Variants:
A man is his own easiest dupe, for what he wishes to be true he generally believes to be true.
As quoted in The Routledge Dictionary of Quotations (1987) by Robert Andrews, p. 255
There is nothing easier than self-delusion. Since what man desires, is the first thing he believes.

“Appearances can easily deceive anyone except a blind person.”

“To write is to read one's own self”
Sketchbook 1946-1949