I recently watched a YouTube video by Michael Bisping a UFC Championship, a very competent ring fighter. He is talking about a situation where he was punched after a short altercation in the street, fortunately, he was not hurt, and to his credit that he did walk away from the situation. You can see the video at https://www.youtube.com/watch?v=VLB6ttxM1Ec.
This does however highlight the difference between sports martial arts and self-defense systems. In competitive martial arts, there is a very formulaic lead-up to a fight. The fight is arranged between two reasonable well-matched individuals (similar weights and skill levels), then there is a lead-up to the fight with the combatants entering into a bit of prefight banter which may include a bit of argy-bargy but nothing that is of real danger to the combatants. The fight happens in a very controlled environment, with a referee who tells the fighters when the fight will start and what the rules are and can stop the fight if anyone breaks them or either party is unable to continue. This is the way Michael Bisping is used to fighting.
The problem with sports martial arts is that it is not how most street fights happen. The fact that an untraining street thug was able to land a blow on him indicates that he was not anticipating the blow even though it was lightly in that situation. He was lucky it was a punch and not a weapon, otherwise, the outcome could have been much worse for him and his family.
Real fights do not have referees, often have unequally matched combatants (gender, physical size, skill levels), can involve multiple individuals and weapons. They can be unpredictable in when they start, levels of aggression, and willingness of parties to be involved.
We train with and without weapons, with the understanding, there may be more than one assailant. We use techniques that would never be allowed in a sport martial art such as gouging, bone-breaking, and joint dislocations.
Situational awareness goes to the heart of the Bujinkan, the most obvious demonstration of this is the Godan test. https://www.youtube.com/watch?v=kGY1eqYRIMI