One reason most people never stop thinking is that mental frenzy keeps us from having to see the upsetting aspects of our lives. If I'm constantly brooding about my children or career, I won't notice that I'm lonely. If I grapple continuously with logistical problems, I can avoid contemplating little issues like, say, my own mortality.
All religious leaders and spiritual teachers emphasize finding a place within us that is true. People who obsessively follow these leaders instead of their own purpose attach to the spiritual leader and become fanatical and controlling. That's why Jesus tried to tell his followers not to get attached to outward form.
Our thoughts about an event can have a dramatic effect on how we go through the event itself. When our expectations are low, it's easy to be pleasantly surprised. When they're not, we're vulnerable to painful disappointment. Because of this, many people spend a good deal of effort trying to avoid developing high hopes about anything.