However, many people who take a self-defense class make the assumption that a 1 week or 3 month course in self-defense is enough practice to be good enough to physically fight off an attacker with effective punches, effective kicks, and effective escapes.
There's an old joke that we had where I worked, it was about a woman who took a 12 week self defence course which involved lots of fancy techniques like wrist locks, judo type moves etc for fighting off an attacker but when the day came much later that she was actually attacked she beat her attacker off with her umbrella.