Post-movie depression?

so, this is probably a ridiculous question BUT does anyone else get really depressed after watching some movies? im going tomorrow night to see the final harry potter installment and im actually starting to dread going because i know that for the next week after seeing it, i will be so depressed. not just because it's over, but for other inexplicable reasons. like i cant even put a finger on what makes me so depressed. and its not just harry potter; there are a bunch of other movies that give me what i call "post-movie depression". i feel miserable for days, even weeks. i obsess over the movie. sometimes i even pretend that i was in it or that i know the cast. i know, wierd. i think i just become so engrossed with the characters and the plot. movies have played a big role in my life, as far as influencing me. why do i have to go through this depression period? does anyone else suffer from this? advice please!