There have a been a number of studies and much research which suggest that these statements are statistically true. In some cases they can be comprehensively explained by the world of science, in other instances the 'how' presents more of a mystery.

People do more when they are happy.
Happy people are healthy people.
Stress is bad for your health.
People who feel in control are happier than those who feel out of control.
Optimistic people get more opportunities than pessimists.
Confident people are more attractive than nervous people.
You can see other people's problems easier than you can your own.
People who can stay calm are more successful than those who cant.
People who take responsibility for themselves feel in control of their lives.
People enjoy praise where it's due and advice when it is needed.
Understanding yourself is the key to understanding others.
We are all prepared to change.
Knowledge is virtually useless unless it can be applied habitually.
We learn best when we learn quickly, and we learn quickly by doing.
To successfully communicate with people we must be able to empathise with their point of view.
Targets that deliver rewards to every member of a team are more likely to be hit than those that do not.
If you want to be heard you have to listen.