a fool's game

An endeavor or activity that is a futile waste of one's time, energy, or resources. Don't you know that playing the lottery is a fool's game? Just a big waste of money if you ask me. It's important to plan ahead, but basing your decisions now on how your life might look in five years is a fool's game. I know you're worried about your kids, but trying to protect them from every little thing is a fool's game.