If there is one skill/attribute that is essential for surviving a real-life assault it is decisiveness. It is also the one key element that can make the difference when you are dealing with someone athletically superior to you. Many people wonder how out-of-shape, older cops and law enforcement operatives are able to overcome, faster, younger, stronger and more athletically gifted criminals. The answer is decisiveness; they don't wait to act - they act before the other person, or at the very first movement, behavior or action a person makes, that indicates that they want to cause them harm. There is the idiom, the quick and the dead. We often take this to refer to athleticism, whereas I believe it should be interpreted as decisiveness, separating those who survive from those who don't.  

As I have gotten older, my hand speed has slowed down somewhat, however I probably block strikes faster now, than I did in my twenties. This is due to the fact, that through training etc. I start my block much sooner than I used to. Having more experience of what someone throwing a punch looks like, means I can identify the setting up of the strike much sooner, and start my blocking movement earlier, thus moving away from the strike sooner, and getting my hand to the arm faster. Good threat recognition/identification along with an understanding of pre-violence indicators, allows you to start working that much sooner. If you can recognize when somebody synchronizes their movement to yours e.g. they start to approach you, follow you, intercept you etc. you can start responding to the threat/danger that much sooner. 

Denial and Uncertainty are the two biggest enemies of decisiveness. Denial comes in many forms. There can be the denial that prevents someone from identifying the real risks and threats that they may one day encounter. The past is a generally good predictor of the future, however it is not absolute i.e. just because you have never been threatened or assaulted before, doesn't mean it won't happen in the future. Bad things don't just happen to other people they can happen to us as well. In studies, it has been shown that when people are given the statistic that the average American lives to be 87,and then asked to estimate, guess how long they will live to, almost everybody gives an answer well in excess of 87 years. Even when people are given the facts, they'll still deny that those facts apply to them.  

Another lesser form of denial, that I see in training, is the type where a student practicing a gun disarm or other technique does so accepting the possibility that they may one day face such a situation but are unlikely to do so. This lessens the effectiveness of their training, as they never expect to have to put what they have learnt in to practice - they are training with the intent that what they are learning is useful knowledge and skills to have but they never expect to have to do it for real. Every time a student trains, they should do so with the intent and understanding that the moment they walk out of the dojo/studio they WILL be assaulted. This form of denial is one of the things that leads students into uncertainty of  action. 

Being able to recognize threats/dangers early and know that they must be dealt with quickly and at the earliest opportunity breeds decisiveness.