What always sounds like a good idea at the time but rarely is?

Going to an expensive brunch buffet. Sounds good at first, cos can have have as much food as you want. But at 40 dollars a plate, you’re either going to leave feeling ripped off or stuffed full of food. Either way you’re going to feel like  vomiting when it’s over. 

Being totally honest when someone comes up to you and says "Can you be totally honest with  me?"