If they don't quit screaming, you do what is called a "walk and peel". If they want something you cannot give like swimming in winter, then you say NO and walk away and peel them off the back of your leg. You do not give in, or argue or try to make them understand. You say No It's too cold and walk away, or No, the popcorn takes 3 minutes to cook, you cannot have it right now and walk away.