First of all you are not the only one... Some of the greatest instrumentalist do have fear of stage too.
I my self have experienced it too at times and some other times I didn't.
The one thing that seems to help a lot is preparation. I know this may sound like a common place but is true.
Now what is preparation??? That's the key. Unfortunately, too many people confuse good preparation with hours of repetition and they are not the same.
Hours of repetition can provide you with a solid ground only if you are doing things right!!! if not???? Beware! because you are repeating your own mistakes and hesitations over and over again.
Another things to explore is the environment and the repertoire you are playing. Are you playing because you really want to or you are playing because you are supposed to be playing there? Are you playing pieces that you love and understand or you are playing pieces that you barely understand and were not even chosen by you? Are the pieces' technical demand at your level or you are barely able to play them?
The reason I ask this question is because most of us have gone through similar situations and the most you are aware of them the better prepared you will be...
For example you are a Junior at a college level and for your Junior recital you have to play a contemporary piece but you like none of those crazy pieces...(I am characterizing here) instead you deeply love the music of Sor, Giuliani, Tarrega, Barrios etc... BUT YET!!! You have to play such piece any way because is a requirement for your degree... The question is... do you think is going to be easy??? How do you see your chances of doing a great job comparing to the choice of playing Barrios' Cathedral? I tell you... is going to be tough and there is a risk that you may even feel that you are not worth of this career... But hold your horses!!! In music degrees/careers there are too many impositions and too little time devoted to explore how to get the best out of YOU and that is one of the biggest mistakes of music institutions (and I talk out of experience)
So, before making this thread last forever I tell you that stage freight has a lot to do with comfort and awareness... If you are doing something that is not that much in line with your will, give your self credit for doing such a thing and be realistic on the results you expect. If you are doing something that you love deeply, do the best you can, be professional about all the minutes you work towards the performance
, Don't leave any details to chance (NONE) and I mean both right and left hand fingerings, dynamics, musical form, style, performance
Finally let me recommend you a couple of books that can help:
The Natural Classical Guitarist by Lee Ryan: ( http://www.*** Commercial link removed ***/Natural-Classical ... 0933224508
The art of practicing by Madelaine Bruser (http://www.*** Commercial link removed ***/Art-Practicing-Gu ... 0609801775
And remember that none of this approaches will work until you attach and adjust to them your own personal story, virtues and defects...
Hope it helps and good luck!!!