Being professionally photographed. The whole 'I will look cool and glamorous' thing is quickly overwhelmed by the fact that it's terrifying and intimidating, especially with the weird lights and the ridiculous lenses. I am not exactly sure why anyone wants to become a model. It seems like it would be a really tiring job.
Reading reviews of your own book. Hypothetically I can think of nothing more exciting! Knowing what people think, after working on the book in a bubble for so long! But then I actually read them and even the good ones just make me feel sort of odd. Like, this is none of my business! If the good reviews are true aren't the bad reviews also true? I shouldn't be reading these!
Going to author parties. But then you sort of stand in the corner (with your non-alcoholic beverage) because your life is a Smiths' song, and really there's just a lot of people trying to impress other people, which doesn't really make for an exciting party at all. Parties are much better when no-one is trying to act cool and keep up their writerly mystique. Also parties are much better when there is fairy bread, which I have not had at a party since about 2004 which is a serious oversight on the part of all party hosts who have invited me to their parties. I think I may be overusing the word party there.
Being a public speaker. When people are being public speakers in films, you always see the end of their speech and their really profound conclusion and everyone clapping and asking for autographs. In real, live public speaking, it's really hard to be cool and relaxed and natural, and say meaningful and inspiring stuff consistently, especially if you're doing an hour long talk. Plus public speakers in films are never depicted getting lost on a sequence of buses and trains as they try to get home, which is what happens to me, generally.
Being an adult. You think, as a child, I'll be able to go where I want and do what I want and stay up late and eat rubbish all the time! And then you're a grown up and you have to worry about earning money and paying taxes and health insurance. And by the time you're done with all that (plus getting an education and planning for a career and investing for your retirement), you're just too tired to stay up late. And I haven't even moved out of home! Imagine how time-consuming being a real adult is going to be.