A revered speaker whom Theodore Roosevelt once invited to the White House, Charles Wagner began as a poor French preacher shunned by the orthodox sect of his church. In his best-known book, “The Simple Life,” he insisted that we control our own emotional fulfillment as much as external circumstances do. Despite the adversity he faced, he found joy by following his internal compass: He started his own church, wrote nearly 30 books, and founded organizations to support the working class. His life is a reminder that your current situation doesn’t have to control you; indeed, your outlook and mindset can change the situation, and cultivate joy even in the most difficult times.