I like this classic quote:
Fool me once, shame on you; fool me twice, shame on me.
Very uplifting; it mostly refers to a specific situation – getting fooled by somebody else; but, in a broader sense, one can get “fooled” by life; it’s somehow life’s fault if it surprises me with something I’m not prepared for; but the second time, it’s only my responsibility.
George BUSH knows this well: