When you suggest something that doesn’t appeal to them, they feel they must assert themselves. Their nature tells them to. They just say “no” in words or actions, even about things that they like to do. The psychologists call it “negativism”; many parents call it “that terrible no stage.” But stop and think what would happen to children who never felt like saying “no.” They’d become robots. You wouldn’t be able to resist the temptation to boss them all the time, and they’d stop learning and developing. When they were old enough to go out into the world, to school and later to work, everybody else would take advantage of them, too. They’d never be good for anything.