When confronted in a dangerous situation, you will experience a high level of stress.  This type of stress will force your mind and body to hone in on the most basic motor skills that associates with survival instinct.
You will experience limitations in your vision, hearing, and motor mechanics.  Your mind and body will perceive anything around you that is not a direct threat as insignificant and drown them out.  You will only focus on the threat at hand.  Be careful, however, because there could be multiple attackers that you cannot see, so it is important you are aware of your surroundings at all times.
If you have ever been in a self defense situation, or a martial arts tournament, you may have experienced that you cannot remember anything around you other than your sparring match.  After seeing video of your competition, you can honestly say you do not remember anything else.  I know I have had this experience.
As much fun as doing fancy kicking drills such as spin hook kicks, 540’s, etc that you do in class, they will be useless.  Unless you are extremely experienced and highly trained, fancy kicks will most likely be the last techniques you will think of employing.  Instead, you will focus on the most basic techniques such as basic kicks and punching techniques.
Thankfully, you do not need to be a super athletic martial artist like Jackie Chan or Jet Li to be able to defend yourself.  It is one of the most basic human characteristics God equipped us with.  Even if you are a child or an extremely uncoordinated and clumsy adult, you can have the ability to protect your life. But, it does take some training and development.  Without formal training, you will freeze up in a hostile situation, and that can cost you your peace or even your life.