Yes. For the best result you should never deviate from it once you decide to use it. If the goal is to just enjoy the game and following rules is not what seems exciting, you can definitely use it here and there without putting too much hope on maximizing payouts. But if you are determined to take the most out of blackjack in terms of returns, learn the strategy by hard and never deviate from it even if you think some hands are better played differently. This requires discipline, perseverance and a great deal of trust. You can’t question the strategy halfway through the game.