The great news is that I am going to share some ideas for FREE. You don't have to take a workshop. As a matter of fact, what I am going to tell you, you can practise everyday and I guarantee that it will be fun.
1. LOVE IT! - If you hate, loathe and despise an activity or song or bunch of people, guess what? You will find it very hard to be enthusiastic. in a choir, you have to enjoy most of the songs. You have to enjoy the process of learning then. AND enjoy sharing them in your gigs. If you aren't enjoying these then you will find it hard to find enthusiasm.
2. IT'S CATCHING - Surround yourself with people who are happy to be there and enjoy showing that. You would call that, enthusiasm. In a choir, you are choosing to be there. So if you are going to be there have fun. That enthusiasm is like measles and you can allow yourself to catch it!
3. FORGETABOUTIT - Leave the nasty workmate at work. Leave the miserable kid at home. Leave your "stuff" in a box and just enjoy the moment. There are times I go to choir feeling less than perky. Someone has said something, or I just feel a bit tired. Once I get into practice and we make some great sounds, all that other stuff is gone. I decide to be in the moment and have fun with the music and those wonderful people who made the effort to be at practice. Enthusiasm is a state of mind.
In the 3 examples above, you will see that being enthusiastic is a choice. When you don't have enough of your own energy, borrow some from those around you. Find the good. It is there. Make it a point to feed others with our enthusiasm when you are up. Let others feed you when you aren't.
Best advice, let yourself enjoy the world in the way of a 3 year old. Don't worry about what anyone thinks but YOU!