Your body language influences how you think and feel about yourself, not just how others see you.

Does our body language govern how we think and feel about ourselves? Evidence suggests it does. Powerful people are more assertive, they tend to take more risks and they are more optimistic than people who feel powerless. This is expressed in body language. Powerful people open up their bodies more and make bigger hand gestures, whereas ‘weaker’ people close up their bodies and make small gestures.

On the physiological level, high powered people have higher testosterone levels and lower cortisol levels. Evidence shows that, if an individual is forced (for whatever reason) to take a leading role, the testosterone levels rise and cortisol levels drop within a few days.

Amy Cuddy conducted an experiment to establish whether faking high- or low power poses will force the body to react. The results show that just posing as if you are in a power position for two minutes, causes testosterone levels to rise and cortisol levels to drop. Using the body language of a powerless person had the opposite effect.

This proves that our bodies can change our minds and can influence how others view us, but also (and more importantly) how we think and feel about ourselves. Once our thinking changes, our outcomes will change for the better as well.

(Source)