“Using ingenious experiments to reveal the brain’s hidden machinations, Wegner and others have found that our brains expend steady, conscious effort to avoid talking about ex-girlfriends on first dates, sending putts off the green, or letting slip the real reason you were late for work. But when our conscious minds are stressed and preoccupied — by, for example, a desire not to screw up — a subconscious process devoted to guarding against the mistake slips through. Unwanted thoughts pop into the forefront of your mind.”