This is a wonderful quote to go into a writer's notebook, and is included in mine. You may think this is a strange, pessimistic remark, but I'd say that only the most fortunate among us could truly deny it. I'm not suggesting that we all have treacherous friends of the very worst variety. Some authors use proverbs for plotting purposes or titles, but they can also trigger off ideas for characters. I offer a selection below, together with my own ideas as to how I might use each proverb to give me a starting point when I was looking for a character to write about, who may or may not turn out to be a main character.
Fools rush in - a set of 'crazy gang' characters in a spoof story.
Beauty is in the eye of the beholder - a character facing up to disfigurement in a partner. Blood is thicker than water - characters involved in family loyalties. Cheats never prosper - a rogue getting his comeuppance. When in doubt, do nowt - an indecisive character, sitting on the fence at important moments. Hope springs eternal - a lovely, bubbly, optimistic type of character.