Why do we fail in many businesses and projects?

Why do we fail in many businesses and projects?    Dale Carnegie's in his book (How to win success ?): There is a high mountain slope in America, the remains of a huge tree, which botanists say lived nearly 400 years ago, in which lightning, tornadoes, hurricanes were exposed, unaffected, and resisted. In recent years, tree has been attacked by a crowd of beetles, making their way to their heart, and they have collapsed in the face of the successive attacks of these small beetles,...

source http://www.alukah.net/web/rommany/0/145660/