This is kind of a lesser known fan theory, but one that I like because it provides *maximum anguish* (lol). Ever wondered why Hiccup lost so much of his leg? Because he didn't recover from it the first time. Honestly, I haven't seen many people utilize this theory but it makes sense to me, given the times.
Also, this WAS originally planned to be in How to Become a Friend, but I decided to cut it because I didn't want things to be too depressing lol. So, yeah, I've always liked this headcanon.
Addendum 3
Things have gotten worse. It's been three days now since we got home, and Hiccup's fever isn't going down. The dragon (Toothless, Astrid reminded me) hasn't been making anything better. It (no, he) has been sick with worry, refusing to eat and hardly drinking. As if it's not stressful enough to fear for Hiccup's health, I have to worry about his dragon too.
Gobber said we'll give it one more day, but if Hiccup doesn't show any signs of improving, we might have to consider taking more of his leg. The conditions from the ship ride and not getting treatment right away seemed to have caused an infection, and if we don't stop it… Hiccup is going to die.
I don't want to have it come to this, but I can't risk losing all of him, when I can prevent it. I'll just keep asking the gods to spare him any more suffering… though I fear it's inevitable.
…
Hiccup did not improve. When I checked on him first thing in the morning, he was just as sick, and I couldn't let it go on. I didn't know how much longer he could take being in such a state, and I couldn't risk losing him altogether. I told Gobber to get Gothi and her assistants, and said they could do whatever they had to do to save his life. And now that it's all over… he's lost most of his lower leg.
I feel absolutely terrible. Hiccup shouldn't have to pay such a high price for my ignorance, my inability to see past my foolish beliefs. It's my fault he's been through ANY of this, all the way from the first day I sent him to the forge when he was six years old. Why couldn't I see him for who he is? Why couldn't I accept him? Why did I believe the only way he could ever be chief is to be… me? I've done irreversible damage to my son, not just physically, but mentally. Reading these pages, it's clear that he grew to think I… don't love him. And that just breaks my heart.
I've always loved Hiccup, even if I didn't show it. I admit, as awful as it is, that there came times when I didn't exactly LIKE him. But I've never stopped loving him. Yet he didn't know that…
Was I truly that bad at showing I cared?
Thinking back on the last four years… I guess I was. All I ever did was push him away, even if in my mind I was trying to help. Odin, I've messed up.
Hiccup believes himself to be a screw up, if I've learned anything from reading about the last three years of his life. But in reality… no one is more of a screw up than me.
-StV
