It is the sadness felt after reading or watching a really long series or story. The bitter feeling when you know the journey is over, but you don't want it to end.
It is the longing for the words on the pages to move for you like they did the first time you read them. When you didn't know what the next paragraph held and the world in which the characters found themselves was entirely without limit. Because any time you re-read the story, you know that they aren't free to roam anywhere like they were before. They are stuck in a cart on a track and all you can hope for is to notice something about the scene you didn't before, and to just try to relive those feelings you had the first time around.
But it will never be quite the same.
This can apply to any series; be it a book series, TV series, an anime, comic, or even movie. The effects can also be felt after completing a stand alone piece that is not necessarily part of a series, although this isn't as common as PSD derives from the attachment one has to the story's characters.
Effects include, but are not limited to:
• A state depression or sadness
• The inability to start another story
• The need to rewatch/reread
• Excessively projecting felt love towards the internet
• Creating fan fiction
- What's up?
> I just finished watching Avatar: The Last Airbender. I feel like I lost a group of imaginary friends. :(
- Yeah, sounds like you've got post-series depression. I felt the same after Harry Potter. It'll pass in a few days. . .