"even the best musicians fluff up sometimes"

My father taught me that the most important thing is not just to play the right notes - you can play occassional wrong notes, and if you keep the tempo going without falter, you will get away with it much easier than stopping, apologising for the wrong note and starting again! Liteners will forgive a few wrong notes, but if you drop the tempo, they are not anywhere near as generous! :-)

So the trick is to learn to 'fake it' or 'vamp' along till you get to where you can pick it up again - this is especially important in ensemble (group) playing - as if all keep the tempo (rhythm) constant, a few dropped notes are not noticed anywhere as much.

Now as to confidence, start in small ways, don't ever rely on props such as drugs (alcohol, etc), just work on buiding your confidence. You could always try a 'public speaking' club, or even some theatre workshops - they will help too.