A person doesn't need to be the tough guy (or gal). When people know your willing to stand up for yourself you won't get in many fights, unless you're wanting to. Yea, you may lose a fight, but if you fight hard, bullies look elsewhere for people to target.
When I was a correctional officer, I knew inmates that were huge dudes, but total cowards. We'd be like "Hey, I would never admit telling you this, but if you do not hit them back, it's never gonna stop". They'd say they knew it, but just could never muster the courage to throw back. Big dudes spending most of their time in solitary confinement of some sort because they never had it in them to hit back despite being giants.