The scientists who conducted this interesting study...
found that our natural sunny or negative dispositions might be a more powerful predictor of future happiness than any specific event. They also discovered that most of us ignore our own personalities when we think about what lies ahead -- and thus miscalculate our future feelings.
people neglect their near selves in favor of their far selves when considering far goals.
Their far selves will most likely have the same basic disposition, even if different circumstances. I think that's the point being made here: that people neglect to think of how they react to events, emotionally (eg. how happy they get when happy things happen) and only think of the events themselves. A future accountant may be happier than a future actor, but neither of them would guess it.