“Some people's affability is more deadly than the violence of coarser souls.”

Shortlist Magazine collects "18 Pieces Of Wisdom From Sherlock Holmes," from which:

• “Education never ends, Watson. It is a series of lessons, with the greatest for the last.” (His Last Bow)
• “Mediocrity knows nothing higher than itself; but talent instantly recognizes genius.” (The Valley of Fear)
• “When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth.” (The Case-Book of Sherlock Holmes)
• “Any truth is better than indefinite doubt.” (The Memoirs of Sherlock Holmes)
• “Work is the best antidote to sorrow, my dear Watson.” (The Return of Sherlock Holmes)
• “Of all ghosts the ghosts of our old loves are the worst.” (The Memoirs of Sherlock Holmes)
• “It is a capital mistake to theorise before you have all the evidence. It biases the judgment.” (A Study in Scarlet)
• “Some people's affability is more deadly than the violence of coarser souls.” (The Adventure of the Illustrious Client) [more]

And while on subjects Sherlockian, I came across this in a collection of "stylish book covers":

 18 Pieces Of Wisdom From Sherlock Holmes Novels - Books - ShortList Magazine