Imagine you're psychic. Make the mental leap that you have the ability to 'see' the value of a card before it's turned over. With this kind of power you could do a lot worse than become a professional blackjack player. You'd never bust, and you'd only lose when your hand couldn't match the dealer's. You'd have a huge advantage over the house and make a load of money.

In the real world, where it's safe to assume you're not equipped with a supernatural sense of prescience, you'll have to make informed guesses as to what the next card will be and play your hand accordingly.