Self-defense is the use of reasonable force to protect oneself from an aggressor. It usually refers to the use of violence to protect oneself and is a possible justification for this otherwise illegal act. Striking, punching, kicking, knee strikes, elbow strikes, along with open handed techniques are employed in self-defense.
Practical applications of techniques are encouraged rather than fancy, flashy movements. Your personal safety is most important. Securing your home and car, walking in safe places, avoiding potentially harmful situations all lead to keeping you safe. Learn to be patient and walk with somebody. Be aware of your surroundings. If you see that you are or might be in trouble, flee! Only if none of the above work must you engage an attacker in some physical way to allow you to get away and get help.
Training in the dojo can be a wonderful way to hone awareness of situations and to build a repertoire of techniques that would benefit you if you needed to engage an attacker.