Are you having performance trouble at the mic? Do you do a great job playing a song at home but then when you play the same one in front of an audience you struggle with it? Stage fright may only be one of the causes of this. The one I'd like to address here is that you might simply be trying too hard. I have a neat little trick here that might help you to correct it.
While recording myself recently I noticed something peculiar that bothered me. Though I was enjoying myself singing and playing, I saw that I had a strained look on my face, like I was toiling through an ordeal. It almost looked like a grimace at times! And I had this look even when I was playing upbeat happy songs - what gives? It kind of shocked me because I didn't feel that way at ALL when I was performing it.
If you've ever experienced this, your problem (like mine) might just be the wrong emphasis - you are trying too hard to perform the song well. Why not try this mindset instead: Just present the song. You don't have to live it, or express all the emotions it displays, just do a good job presenting it instead. Deliver it clean and correct. If it is a powerful song that evokes intense emotion that will naturally transmit to the audience without all the "histrionics". So just hold a professional, courteous smile when you play, concentrate on the delivery but don't try to do a performance. As you get better you might get more expressive in your delivery, but that'll come later.
Another tip: Dont put any undue pressure on yourself. If you're a little nervous or even if you make a minor error or incorrect note don't worry about it, you're HUMAN. In fact, if you do screw up but have the courage to recover strongly they might even respect you more than if you didn't. Just concentrate on the job at hand and PRESENT that great song with a smile!