"I'm just an introvert"

You may have settled on this as the explanation. You're an introvert. Introverts find company draining and need time alone. So staying in is simply you honouring your nature, and a book telling you to go to parties has misunderstood who you are.

I agree with a good deal of it. Introversion is real and it isn't a fault. Some people prefer small groups to large ones, one long conversation to six short ones, and a quiet evening after a busy day. If that's you, nothing here asks you to change it. You can build a social life out of dinners for four and walks with one friend and never go to a loud party again.

But introversion and nerves are different things, and they call for different responses. Introversion is a preference. It says, I'd rather do this than that. Nerves are a fear. They say, something bad will happen if I go. You can have either without the other. There are nervous extraverts, who long for company and dread it. There are calm introverts, who go to the party without a flutter, enjoy an hour, and leave because they've had enough.

You can tell which one is operating by how the refusal feels afterwards. When an introvert turns down a big party because they'd rather read, the evening in is a pleasure. There's no weight beforehand and no drop in the stomach at eight o'clock. When nerves turn it down, you get the pattern from chapter 1. There was dread beforehand, a rush of relief, and then a flat evening and regret. Look back at your list of ten invitations. For each one you refused, ask which pattern followed, and you'll be able to tell.

The label can also hide things from you. Once "I'm an introvert" is the reason, you no longer ask whether you wanted to go. You wanted to go to those leaving drinks. You said yes within a minute.

Zelenski's studies from chapter 5 are relevant here. His introverts expected to dislike behaving sociably, and then enjoyed it about as much as anyone. In related experiments his group found that acting in an outgoing way raised introverts' mood without raising their negative feelings. They found no sign that acting that way tired the introverts out on a test of concentration afterwards. Again, this was in the lab and over short periods, and an hour in a lab isn't a wedding weekend. But it suggests that what introverts expect from company can be worse than what they get.

I'd go along with the label as far as this. Let your introversion choose the kind of event and how long you stay. Choose the dinner over the club night, and go home at ten if you like. But when you wanted to be somewhere and nerves are the reason you're not going, that isn't introversion.