Do You Believe in Magic?

So I've successfully escaped one Siren's lair. I've boarded my ship again, and continue to sail further into the unknown. Along the way, some of my crew mates tell me things meant to be private were not kept as such. Instead of stewing, as I was wont to do, I realized that in such a confined space it would accomplish nothing except unnecessary grief. I forgive him, and we continue on in relative peace.

We see an island up ahead. What's on it, we don't know. I can't tell from here; all I see are rocks and the silhouette of what seems to be a castle. The closer we get, the colder we get, until we've all huddled under blankets. Hearty explorers never pass up a chance of discovery, so I bravely disembark the ship and climb onto shore. I finally realize what that castle is: a prison. Not just any prison, but Azkaban, the wizarding prison from the Harry Potter universe (all things Harry Potter-related belong to J.K. Rowling, I'm just a lowly obsessed fan). Soon after realizing this, we board the ship again and sail away, fortunately not running into any dementors in the process. I wonder, though, about these foul creatures.

I wonder what my worst memory would be? Since dementors make you re-live your worst memories, I don't know which mine would be. I have a feeling I know what it would be, that it would involve a certain person and a certain activity, but what if I've repressed these memories, as I feel I have? Can dementors make you relive/remember repressed memories? And if not, I don't think I have many things besides for these repressed memories that I could potentially drown in the memory. I may feel like I'd never be happy again, like some of the characters, but I don't know if there is any memory that could so strongly affect me.

In Prisoner of Azkaban, I'm at the part where Harry is about to face the boggart, and he thinks of a dementor. This got me thinking: what is my worst fear? What shape would my boggart take? I know my greatest fear is dying unloved, but how exactly would it be able to show it? I'm afraid of lots of conceptual things, not really spiders and clowns and whatnot. Seeing these probably wouldn't scare me too badly, unless a huge spider like the one they made in the movie popped up. And then, I know I could easily overcome that, because that's more gross than anything. I'm afraid of heights. How would that be conveyed? Me falling off a cliff? Any ideas as I slowly sail back into the unknown?