I like this one. It reminds me of my sense of humor...
"Your chief trouble is that you think you've got a sense of humor. It confuses people, and you ought to get over it. Things strike you as funny. It may be all right this time, but some day something that you think is funny will blow your goddam head right off your shoulders."
Only after he had gone did it occur to me that that wouldn't prove it wasn't funny.
-In the Best Families by Rex Stout