A Promise Is A Promise

I think promises is are meant to be kept.But some promises cannot be kept because they may be impossible.If I were Aurelius,I will keep my promise and give the magician a thousand pounds.But who knew that Dorigen's husband came back without his ship destroyed by the rocks.So I broke my promise and could not pay the magician a thousand pounds.Luckily,the magician listened to my story and did not ask me for the thousand pounds.So that is why some promises are meant to be kept but some are not.