Two videos demonstrate the importance of staying alert and being prepared to ramp up quickly to a combat mindset.
First video shows an elderly lady with combat mindset:
http://www.liveleak.com/e/732_1231826915
Second video shows a young man caught off guard, though he carries a gun for a living:
http://www.liveleak.com/e/11b_1210344827
H/T to Ignatius Piazza:
