I don't think nerves should ever put anyone off from singing and/or playing. Neither should the fear of messing up on a song or fear of what those in the audience might think of you or your presentation of a song. Being 'backward at coming forward' so to speak, stopped me for years. Now, in my fifties i'm inclined to think 'sod it' and just have a go (occasionally) and i've not bin booed off (so far). Now i wish i'd done it years & years ago. As Martin Carthy once said in an interview:
'I've had an audience for 40 years that would pay and listen and let me walk up blind alleys, fall flat on my face and make a fool of myself, learn things, unlearn things, try another way. They've allowed all of us to do that. Can you think of a better reason to do something?'