Take a "power posture"

2 minutes of power posing - standing tall, holding your arms out or toward the sky, or standing like Superman, with your hands on hips - will dramatically increase your confidence.

Try it before you step into a situation in which you know you'll feel nervous, insecure, or intimidated...

Powerful people tend to be more assertive and confident, more optimistic. They take more risks. 

Studies showed that a two-minute power pose leads to hormonal changes that configure your brain to be either assertive, confident and comfortable, or stress-reactive.

Negative arguments have a harmful effect on our brain. 

When you discuss any particular issue, make three positive comments for every negative statement.  It will create opportunity for a more constructive dialogue.