Dad has been making Christmas Puddings. When you make a Christmas Pudding and stir it, you can make a wish. Like many wishes, if you tell anyone about it, the wish won't come true.
Logically you can game this by wishing for something you DON'T want to come true, then tell everyone about it. This of course can't work; by the nature of magic and wishes, a wish must be made with all your heart. Wishing for something you don't want can only have bad consequences.
But what if you wish for something you truly want, then change your mind? Breaking a wish can't be good, but if the wish would cause damage, what are you to do?
If I believed in this stuff, it would make for quite a dilemma. I played safe and wished for something personal to me.