If a potential attacker sees by your body language that you are not an easy target, then they may change their mind.
People subconsciously take in and believe more in body language and the tone of the voice, than the actual words spoken.
Practise being strong and assertive in your manner, without being rude, aggressive or arrogant. Use facial expressions, gestures and posture to get your message across. Even if you feel cold, tired or unsure still walk and stand tall, look confident and alert.
Be more aware of other people's body language so you may be able to predict their intentions. Practise self-defence techniques without giving a pre-warning with your body language.