LOL
I feel your pain, for me i find it super annoying when someone walks up to me when i'm drawing and just says something like "Hmm, the nose looks bent", so recently when anyone walks up and catches me on an unfinished work, i expect a negative comment, so I end up freaking out even before they say anything.
How i deal with it? Well i just close my book and make conversation until they're gone or just call it a day...[not really helpful...sorry :D ]