I know it feels counter intuitive but the Harvard Business Review just published an interesting article on exactly that theme, explain why it can help you reach your goals, personally or corporately.
Tellingly, I also read an article in Psychology Today which said that people who never take risks, who never try something tough find that their comfort zone shrinks. As they do less, they feel less confident and their ability to take a risk reduces too. So the result is a vicious circle. And their world literally gets smaller as they turn down opportunities to grow.
And the 'fix' for this malaise is simple; Do something difficult, something the pushes your comfort zone and challenges your status quo. Do that thing you've talked or dreamed about for years and do it with passion and verve and remember what J K Rowling said:
"It is impossible to live without failing at something, unless you live so cautiously that you might as well not have lived at all - in which case you fail by default."