In uncertain times, individuals who are constantly prepared to face a variety of challenges are far more likely to succeed than those who simply react to the ever-changing circumstances. This sort of preparedness requires mental discipline, and it can facilitate the making of sound instantaneous decisions when disaster or unexpected events suddenly strike. Characters who must remain alert because of the nature of their lifestyles are often particularly vigilant. This includes those who live within hostile environments— either urban jungles or dangerous wildernesses—and those who live as professional soldiers.