I fully agree.  An optimistic team is better, and even more important an optimistic leader is to achieve excellence!

The Optimistic Team for Project Management Success

About 100 years ago, Ernest Shackleton was looking for a crew for a challenging project: to produce a map of the South Pole. It is said that he published an ad in the local newspaper looking for team members with creativity, a good sense of humor and technical skills.

Fast forward to the present day. Dr. Martin Seligman, director of the Positive Psychology Center at the University of Pennsylvania in the United States, is the founder of positive psychology, which focuses on the study of such things as positive emotions, strengths-based character and healthy institutions.

Dr. Seligman theorizes that in order to choose people for success in a challenging job, you need to search for aptitude, motivation and optimism