The article basically describes the planning fallacy. People imagine, and thus expect, the best possible circumstances and are consequently surprised when reality falls short. In that sense, positive thinking isn't always the best, but then neither is negative thinking. The solution is simply to think rationally. While positive thinking is nice, in reality such is detrimental to achieving our goals. As for fantasizing, all things in moderation. Fantasizing allows us to see beyond the realm of possibility. At its best, it nurtures imagination and fosters hope. Allowing- just briefly- yourself to imagine what life could be, paired with rational goal setting, is what separates the day-to-day achievers from the entrepreneurs. After all, generations of humans had to fantasize over flight to one day invent the airplane.