I have observed, in the course of a dishonest life, that when a rogue is outlining a treacherous plan, he works harder to convince himself than to move his hearers.

-Fraser, George MacDonald
  Flashman.

All the arguments which are brought to represent povertyasno evil, show ittobe evidentlyagreatevil.You never find people labouring to convince you that you may live very happily upon a plentiful fortune.

-Johnson, Samuel known as Dr Johnson
  Remark, 20  Jul. Quoted in  James Boswell The Life of Samuel Johnson (1791), vol.1.

There is a holy mistaken zeal in politics as well as in religion. By persuading others, we convince ourselves.

-'Junius' possibly the pseudonym of  Sir Philip Francis
  Public  Advertiser,19 Dec, Letter 35.