Did you know the etymology (origin; root) of enthusiasm is: "possessed by a god, inspire." [en-, in + theos, god] (New World Dictionary) That fascinates me. The literal definition of enthusiasm is to be possessed by (a) God. Looking at it a different way, consider the antonyms (opposites) of the word; apathy, indifference, half-hearted, listlessness. Is it just me, or doesn't that provide a clue as to how we could conduct ourselves?
Okay, I can hear you now--"Dude! give it a rest, already. You talk about God too much." Fair enough. Even though I've said I don't care if you believe in God or not, (and I don't) lets look at it from a different point of view. Watch this 2 minute and 57 second link;
No word about God was there? Just a practical approach to improving your life. The emphasis of what she is promoting is a gratitude list to be thankful for. From a LIFE COACH no less! And what Sarah suggests will increase your enthusiasm (possessed by a god) is to be grateful. (see life as gift) Where we differ is that I contend that an ASPECT of God is revealed in the process. If we take the literal definition of enthusiasm, we are privy to an aspect(s) of God (energetic, vigorous, passionate, warmth).
Application: For one week, try the following. When you get up in the morning repeat: 1) I will greet this day with love in my heart. [~Og Mandino The Greatest Salesman in the World] 2) Sing (or what passes as singing for you) Oh what a beautiful morning-Oh what a beautiful day-I've got a beautiful feeling-Everything's going my way. [~Oklahoma! Rodgers and Hammerstein] 3) Do your best to believe it. 4) See what happens.