Here's something to think about. LIVE IN THE PRESENT. If you decide to sing in public, you must do it to enjoy the moment. It is a collective joy for you and your listeners and not an anxiety filled experience.
I have found that my initial nervousness has been chanelled into an adrenaline rush as I take the stage to enjoy performing what I consider to be meaningful songs appropriate for that audience. Have this confidence. Folk singers are always prepared with a repertoire much better than singers in other genres. I have enjoyed many barely acceptable voices singing interesting songs. Besides, you can chat up the audience to relieve some of the tension. They want to know about you, your experiences and why you are singing that song.
One other thing. A good performance lies somewhere between emotional outpouring and control. Don't get completely carried away. YOU ARE IN CONTROL. This is your gift to your audience.