When Alexander was only eight or nine years old, he tamed his first horse that none of his father’s grooms could manage. Alexander had noticed the horse, Bucephalus, acted wild because he was afraid of his shadow. By speaking to the horse gently and turning him to face the sun, Alexander was able to ride him. Seeing this Philip told his son “you will have to find another kingdom; Macedonia is not going to be big enough for you”.

source: World History