A large portion of the weekend effects is explained by differences in the amount of time spent with friends or family between weekends and weekdays.
Daniel KahnemanMood evidently affects the operation of System 1: when we are uncomfortable and unhappy, we lose touch with our intuition. These findings add to the growing evidence that good mood, intuition, creativity, gullibility, and increased reliance on System 1 form a cluster. At the other pole, sadness, vigilance, suspicion, an analytic approach, and increased effort also go together. A happy mood loosens the control of System 2 over performance: when in a good mood, people become more intuitive and more creative but also less vigilant and more prone to logical errors.
Daniel Kahneman