Why hello there! Baby Hiccup time is gonna be fun. Thanks for asking… thinking about the Hooligan as a little tike usually brings me into a happy smile. :3
I’m no psychology expert in the children’s area, regrettably, but I feel like lots of kids have fears when they are very young that they just grow out of naturally over time. It doesn’t have to take a big event for a young one to learn not to be afraid of the dark, to give an example. Sure, sometimes there’s a significant event that ends the fear, but sometimes it’s just a simple growth in psychological maturity that leads a kid to move forward.
And if you think of infanthood and toddlerhood, those age times that people almost invariably forget as they age (thus probably Hiccup’s age during his fear), just about anything can scare them. Novel events can make a one year old or two year old cry with little provocation. I mean it could just be a cat walking into the room that startles them, and then they become afraid of the family cat, but as they grow older, there’s no enormous personal growth breaking them out of the fear. They get older and just like that Kitty isn’t scary anymore. That’s just a factor of their maturity, so it could have been so with Hiccup and dragons.
I guess I’ve always headcanoned Hiccup’s childhood - or rather toddlerhood - fear of dragons to be something like that. There was just a tiny little boy who was given a toy that looked SCARY and it looked like bigger SCARY things so he cried. But as he grew older, he naturally would have looked at things like dragons with a bit more knowledge and not had that instant cry-and-be-frightened reaction.
I also think his drive to be accepted by his father didn’t start at THAT young of age. I mean, yes, as a very young boy he’ll definitely undeniably absolutely desire his father’s love. But I imagine that it’s as Hiccup grew older and became more and more different and outcasted, his relationship with his father worsened. Young teenagerhood would be the time Hiccup and Stoick can hardly even speak to one another because they cannot get along, and that’s the point where Hiccup’s drive for acceptance (a huge psychological issue for teenagers according to developmental studies) leads him to do his crazy stunts a la movie one.
Although, if you think about it, Hiccup still retains a healthy fear of dragons even as he grows far older. It’s not what Stoick’s talking about in “Breakneck Bog,” but it’s fun to think about: Hiccup was scared of dragons as a teenager, too. That’s normal instinct at this point of development. Dragons are enormous fire breathing beasts that destroy houses and maim and kill humans. Hiccup and basically all the Vikings have a natural fear of dragons simply for survival reasons. It’s not until Hiccup and Toothless befriend one another that the fear leaves completely.
And at that point in time, I bet it’s awing for Hiccup to think about the fact that yes, he used to be afraid of dragons. He used to be chased by them and run away from them and flinch when even an adorable, warm-hearted Gronckle neared.