Have you ever noticed that, however famous they are, some sayings don't make any sense at all?
Take the saying, "never say never". In that phrase you have just said never twice and the sentence is just pointless.
Or how about "expect the unexpected". If you expect the unexpected the unexpected becomes expected and so then you'd have nothing to expect because the phrase says expect the unexpected not the expected.
Then there's the famous line your parents give you; eat your food because their are tons of people starving in Africa". What the hell do poor people in Africa gain when YOU eat the food?!?! In that case just give the food to them!