I also feel that situational awareness is important, but mindset is the number one for me. I've had to run for my life before, NOT FUN! I used to have to walk through some pretty rough areas as a kid in Massachusetts. The mindset is important in ANY self defense situation. My options as a kid were pretty limited, fist fighting, or running my ass off. Since I was a fast kid, but skinny and not much in a fight, I decided pretty early on to run my ass off if that option was available.
Here's where physical fitness comes into play. Fat kids who wouldn't fight were usually the targets of choice. They'd normally never fight back (lack of the will to win) and they didn't even really HAVE the option to run (lack of physical fitness due to hours in front of the TV).
If you think middle school and high school bullies are a different animal than your common thug bad guy, think again. They have many of the same motivations and tactics.
SA has kept me from several beatings. I had the ability to see high threat areas and potential ambushes and avoided them. In some cases, the difference between a beating and a cold stare was simply crossing the street at the right moment. Physical fitness ALSO kept me from a few beatings. The ability to play track star is a GREAT option to have. Options are nice to have, even if you never need them. Better to HAVE it and not need it than NEED it and not have it.
You also need to have the ability to be one mean dude. I got out of a crappy situation in which I was being robbed at knife point in 9th grade by telling the dude with the knife to f*** off in a mean voice. Bad guys don't typically like a target that fights back, especially when there are much easier targets lined up. This goes to mindset, as well as situational awareness. You need the SA to make a sound judgement call on when to do what, and the mindset to actually tell someone putting you in a bad situation where to stick it.
Another factor of SA is knowing things ahead of time, such as who resides in certain neighborhoods. I was able to avoid some nasty situations by simply being in good with the right people in the right neighborhoods. This may not be an option for most people, but it was certainly nice to be able to get along with people who resided in these neighborhoods and have people I knew there.
Now, I don't mean to come off as a badass or anything, but these are my experiences from before I escaped the People's Republic of Massachusetts.