It's not EXACTLY post-series depression...but I seem to remember that the British term for "Season" seems to be "Series", so if we extend that, then it's applicable.
One day, I sat down to watch the season finale of both Dexter and Californication. I was loving Dexter and then at the end...
Dexter found his wife, murdered in her bathtub by Trinity, his baby boy covered in her mommies blood, just like the events that led to him becoming a serial killer himself
That bombshell...and I relized that I will have to wait until the next season to go anywhere with that...damn. Well at least I have Californication, Season 3, and...
Hank Moody finally lets his wife know that he slept with her ex-fiancees underage daughter. She turns a 180, from rebuilding there family to hating Hank, hitting him, their battle being dragged out into the street, which leads to Hank punching a cop. Then BAM, episode ends
Wait, what? He did THAT? It was far too much to leave unresolved. I'm still recovering.