Feedback is always welcome :) HTTYD doesn't belong to me at all; I haven't read the books, so apologies if this diverges massively from anything you're told in them.

Sometimes something happens that completely changes how you think. Sometimes it's something big, dramatic – the kind of event that shifts the world, changes everything. And that's happened to her too. But sometimes, it's something small.

In Astrid's case, it was a sprained ankle.

She was in a bad mood. She'd fallen the day before, and now even standing was agony. She still hobbled around, flatly refusing to sit in bed all day long. What she had forgotten was that she was going to have to sit out on just about everything. Morning lessons were fine, sat in the great hall with the other kids her age. It was the time after, when they ran around playing tag, showing off to each other their skills with the small weapons their parents were teaching them to use. She had to sit and watch.

Astrid hated it. At the age of seven, being made to simply watch while your friends play is its own brand of torture. For a while she was judge, while they held sprint races. Then it degenerated into a free for all, and she was back to being bored on the side-lines.
She watched grumpily while they played tag. She was good at tag. Astrid was good at anything she set her mind to. Hiccup, on the other hand, was bad at everything. Snotlout was declaring as much, and she couldn't help nodding in agreement. Then she noticed Hiccup nodding too, looking at the floor. He actually agreed. She sighed. Vikings didn't do that. If someone said you were useless, you showed them you weren't. By using their face as a hammer if necessary. But Hiccup just stood there and took it. And Snotlout just walked all over him. Everyone did. The game restarted, and Hiccup wandered off, looking…well, looking hurt. Then, even as Astrid watched, he straightened up. He still looked a little bewildered, a little sad, but he didn't look defeated anymore. Her attention was called back to the game by a shout, and she jumped when Hiccup tapped her on the arm a few minutes later. She glared at him, almost instinctively.

"What do you want?" He held something out, looking rather like he wished it were a shield. "What is that?"
"It's a game." His voice had a nervous squeak in it, but he relaxed a little when Astrid didn't tell him to go away. He set it up, and showed her how to play. Two little Vikings on a scratched out grid. A handful of dragons, and some dice. He had to explain the rules twice, but she picked it up quickly. Pretty soon she was thrashing him. He just smiled happily at her, much more at ease than when they were all running around pretending to kill each other. Or to kill dragons.
"You're smart, you know."
"Huh?"
"You're smart. You're good at thinking."
She wasn't quite certain why she said it, at the time, but later she worked it out, though it was years before she put the words to it.

Astrid had always known who she was; she was tough, and strong, and she was going to grow up to be a dragon slayer, protecting the village. Even at seven, she knew what she was.
Hiccup didn't. He wanted to be something that he wasn't. Even his own made up game was about being a big strong Viking.

And that was another thing.
He was letting her win.
It took her a while to notice. She was used to being good at things. He was deliberately not making the best strategic choices, warning her when there was a better move she could play. It sort of annoyed her. But it was also sort of nice.

Vikings weren't always good at nice.

Years later, she thought maybe she should have tried harder at nice. After that day, she cut back on mean, a little. She was silent when others mocked. She sighed when others laughed. She tried to ignore, while others exploited mistakes.

But time passed, and Hiccup still wasn't certain who he was. They trained, and she was torn between helping him, and giving up on him. She saw what Gobber knew, what Stoick must have known – if Hiccup went into the real world, he'd be dead in seconds. So she scared him. He had to decide, he had to learn. He had to either become the Viking he wanted to be, or accept that it wouldn't happen.

Then he did. Gradually he overtook her, dragons falling before him when before he'd been cowering from them. She hated it. Hated it because he was the weakling, and she wasn't, and he was better. Hated it because it took away everything she had planned for. Hated it because she wasn't used to losing. And hated it because he didn't seem to know he was winning. He didn't seem to realise that there was a competition. That was the worst thing. If he'd been victorious, basked in the glory, it would have been easier. She could have hated him, then. But he simply didn't see. There was just bemusement, like it hadn't occurred to him to think that he would become celebrated, despite how much time he had spent on hare-brained schemes trying – and failing - to impress everyone. He disappeared every day, and she couldn't find out what he was up to, what had changed about him. He didn't seem to see that they were competing, that suddenly and inexplicably he was winning and she was losing.

And then she met Toothless, and she understood why.
Hiccup had finally found out who he was, and had accepted who he would never be.
Hiccup wasn't a dragon killer; he was a dragon rider.

And as she floated through clouds and saw her whole world spread out below her, Astrid thought that maybe the person she knew she was wasn't quite who she wanted to be after all.