This is an old one, from Matthew Collings’ book, Blimey:

“Private views are emotionally quite intense, although the emotions are never expressed, they just go on in your head. On the outside you appear normal and go around saying Hi! brightly, or, Hmm, that’s interesting. But inside you are reeling. The shocks come fast and hard. Regular private view goers have disintegrated personalities and are suffering from post-traumatic stress syndrome.”