There is an expression in the German language, einmal ist keinmal. It literally means, one time is never. It is used to mean that it's ok to make a mistake, because if the mistake happens just one time, it is of no consequence and really doesn't matter. But I really can't get my head round this - the sentence is a paradox and a complete contradiction of terms... it's like a thing denying it's very existence... if something is once, it means that it exists and it can't undo itself and not exist... also, the idea that something can be of no importance because it only occurs once is nonsense... there is only one planet currently known to harbour life. The Earth is unique, einmal. Does that mean that it shoul have no importance? To me, that fact that something can exist if even just once is of huge significance.