Yesterday we visited the topic of stress inoculation. Deciding before hand where we will draw our line in the sand and building skills to the level that they become habits allows us to spend important mental power on solving the unique aspects of a particular problem (being robbed, or otherwise assaulted) instead of trying to figure out how physically respond.
The ability to issue verbal challenges/commands and to get your weapon into play (if needed) without thought allows us to move through the OODA loop faster than our adversary. This equates to survival.
Proper training is a huge tactical advantage and is the cornerstone of efficient (life-saving) behavior. Although the forgoing is a gross over simplification, it is accurate and should stimulate your desire to delve deeper on your own.
PHOTO: By Patrick Edwin Moran - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=3904554