Buck utilized System 2 of his cerebrum to figure his exercise plan, yet then surrendered to System 1 when he chose to sleep in.
System 1 and System 2 are two particular methods of decision making: System 1 is a programmed, quick and regularly oblivious state of mind. It is self-governing and productive, requiring little vitality or consideration yet is inclined to biases and methodical blunders. System 2 is an effortful, moderate and controlled way of thinking. Which explains why Buck chose to sleep :)