For the secular, let's try a philosophical approach to capture the essence of this virtue. In the Buddhist philosophical tradition, the equivalent of enthusiasm is "Virya", which is also known as the Paramita of joyous exertion. This paramita is associated with the qualities of vigor, vitality, endurance, diligence, as well as continuous and persistent effort. When we firmly anchor ourselves in Virya, we can view failure as a step toward success and danger as an inspiration for courage. This would be in keeping with Emerson’s description, and as Winston Churchill said: “Success is the ability to go from failure to failure without losing your enthusiasm.”
If the religious and philosophical approaches are not satisfactory, then where else can we turn to understand and incorporate this virtue into our daily lives? How about Walt Disney, who encouraged us to "Whistle while [we] work" in the animated film, Snow White and the Seven Dwarfs. I can offer no better advice for enthusiastically going about our daily affairs.