Hi housecat,
It is different for everybody, and I don’t know if there is a formula that increases enthusiasm. Perhaps try to get involved in something that you find interesting.
Antidepressants can help, but they do not treat the depression. They just suppress the symptoms so life becomes a little more bearable, as you have recognized.
What about exercise? Moderate-intensity exercise has antidepressant effects, raises energy levels, motivation, and a host of other benefits. This, in turn, may increase your enthusiasm in general.
Diet is also critical for health. If you include nutrient-rich foods (fruit, vegetables, meat, fish, legumes, etc) in your diet, this will give you more energy and stablize brain chemistry. Again, in turn, this will affect your mood and enthusiasm, as mind, body and the nutrients we absorb are all interrelated.
Establishing a routine may also help.
Try writing down a list of things you want to accomplish. Or even a "to do" list can be useful, so you have focus and drive to accomplish something in a day.
What about spending time with friends and family? Do you know anyone who is energetic and enthusiastic? Spend time with them and their motivation, energy and enthusiasm may rub off onto you! Also, talking to other people who share similar interests will create and fuel enthusiasm.
Music may help, as it influences our mood and energy levels.
Certain movies may give you a boost in enthusiasm.
You can also watch motivational vids… these will give you a MASSIVE, short-term boost in motivation and energy, which in turn give you a boost of enthusiasm. I will leave a link to a few to get you started…
Dream--Motivational Video:
https://www.youtube.com/watch?v=g-jwWYX7JloContenders--Motivational Video:
https://www.youtube.com/watch?v=YDSwwEeF_K8Hero--Motivational Video:
https://www.youtube.com/watch?v=cZjtRQMEOmI