Holiday repeatedly reminds readers of the importance of the Stoic concept prohairesis, or reasoned choices. By focusing on one’s own agency and ability to make rational decisions, Holiday promises that readers will be better able to create happiness and stability in their lives. Explaining that “The single most important practice in Stoic philosophy is differentiating between what we can change and what we can’t” (9), the author maintains that many people waste their time worrying about external events or possibilities that they cannot influence. Instead, they should redirect that energy.

Holiday uses quotes from Stoic greats such as Seneca and Epictetus to show that reasoned choices should manifest in our lives as consistent discipline and the ability to resist harmful habits. As Seneca writes in Moral Letters, “We must give up many things to which we are addicted, considering them to be good. Otherwise, courage will vanish, which should continually test itself” (16). Holiday adds that only reasoned choices can keep habits from “running our lives” (16) and undermining our freedom. He underlines this point by telling readers “we are studying philosophy precisely to break ourselves of rote behavior” (24).