system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Dreams. Why sometimes the dream is so vivid that we get that "Damn it was just a dream" feeling?

Trying to make it more clear: I had this really nice dream last night. And was kinda sad for me waking up to realize that I was in fact just dreaming.
gpt
You're going to get lots of 'experts' giving self-assured reasons why. But any question about dreams is like a dream itself - we just don't have confident answers yet because we don't really understand dreams well, or even the brain itself for that matter.