system
Given the following post, respond as if you're commenting on Reddit:
human
Why is it so difficult to remember dreams?
gpt
Disclaimer: This is probably not the whole reason. 

Memory is state dependant. Sleep is an altered state of mind, so memories from sleep are easier to access when you're in that state of mind. The same thing happens when you can't remember anything from last night because you were so wasted; if you get mildly drunk the memories will come back easier because you're re-entering that state of mind.