HSC stories are usually subjective to the paper; in my year it had to be related back to the overall 'theme' of the paper that far (can't remember what it was, it was three years ago).
If you're doing Inner Journeys, it's usually related to self-discovery. As has been said, chronic illness does just this, but I think it's over-used and over-rated. Personally, I'm a fan of the 'struggle within' route, where a person has to deal with their inner demons. That's also over-used as most people willwrite it about drugs, suicde or depression, but there's a hell of a lot you can do. Mine was literally about inner demons: my main character was a modern-day cowboy who had been possessed by a demon. He and his friends witnessed an angel falling from the sky who was kidnapped by a band of villagers (they had just found out about the hero's possession, so were in fear of anything like that). The hero liberated the angel, even though he was host to a demon, stating that the will to live was what kept him sane. His soul had been destroyed when the demon took control of him (I never had time to explain hos that happened in the first place), so nothing that he did made any difference to his ultimate fate: he would not get to experience the afterlife. But he believed that since nothing he did mattered, the only thing that mattered was what he chose to do. He could easily terrorise the world because he was no longer human, but he still chose to do some good regardless. The angel offered to prolong his life as a reward (nothing could resotre his soul), but the hero declined; he already had the demon for that. The inner journey was that good and evil were simply names we gave to our choices, but the will to live and the power of choice were far stronger than either.