What determines how much a thought occupies our mind. We like to think we have so much control over our thoughts and our behaviors, yet sometimes it seems like we have no control at all. Thoughts can keep us up at night and consume our attention almost to the point of paralysis. Is overcoming this simply a matter of willpower? Can we control it? And why do some thoughts that once occupied our mind, lose their power over time? Perhaps its our curiosity that drives it, and the not-knowing makes it harder to let go.