Love interest nearly always weakens a mystery because it introduces a type of suspense that is antagonistic to the detective's struggle to solve the problem. It stacks the cards, and in nine cases out of ten, it eliminates at least two useful suspects. The only effective love interest is that which creates a personal hazard for the detective - but which, at the same time, you instinctively feel to be a mere episode. A really good detective never gets married.
Raymond ChandlerEverything a writer learns about the art or craft of fiction takes just a little away from his need or desire to write at all. In the end he knows all the tricks and has nothing to say.
Raymond Chandler