Stand up straight.
Standing upright not only makes you feel more confident, but it actually decreases stress hormones. A recent study in the journal Health Psychology found that people who had a slouchy posture while performing high-pressure tasks reported having more negative thoughts and feelings than those who sat upright. Other studies by researcher Amy Cuddy show that standing with an upright posture increases testosterone and decreases levels of the stress hormone cortisol. This seems to cause people to feel less anxious and more assertive and confident.Source