Have you hated someone you know was better than you and would take you out anytime you try to take him on?Yes, i know that, but how would you know Sasuke was scared of Itachi? Sasuke was scared of Itachi for a moment in the manga and that's when he out of power and Itachi pulled the Susanoo.
Deep down, its fear of being beaten that makes you grow stronger. Exactly what happened between Sasuke and Itachi