I'm a firm believer that most "heroes" are simply people who were in the wrong place at the wrong time and managed to avoid panicking. What are your choices?
1. Pull girl out of path of bus.
2. Freeze, or scream and wave your arms over your head in panic as bus hits girl.
3. Dispassionately watch bus hit girl.
4. Rejoice in your luck as you enjoy watching bus hit girl.
5. Push girl in front of bus.
The majority of people will say they would do 1, but in reality would do 2. The few who actually keep their heads long enough to do 1, we call heroes. Three, four, and five we call deranged.
Historically, I've been one of those who didn't freak out and did the obviously right thing. And I'm no hero. I just don't tend to panic.