8.

People can unconsciously feel the emotions of those around them. We naturally mimic others' movements and facial expressions, which in turn makes us feel something similar to what they're feeling.

If you're generally upbeat and enthusiastic, other people will feel ...

... or ironic and don't complain all the time. 

All of these behaviors are people repellent. We naturally gravitate towards people who are kind, loving, cheerful, and funny, rather than to those who complain all the time.

Research suggests that happiness and optimism influence positive life outcomes as much as it is a byproduct.

In a study, enthusiastic, cheerful people experienced less memory decline with age. A positive outlook boosts immune responses while reducing the likelihood of ...