You know when you're trying to fall asleep and your brain just goes "what if..." Yeah when that happens I get out of bed and just write the beta version of a chapter (sometimes I'll stay awake until 4 in the morning).
Then, when I'm actually awake enough to look at what I wrote and go "What the fu..", I make some changes, clean it a little bit and save the file.
Boom, one chapter.
So yeah, if you're ever struck with inspiration, don't ignore it just because it's 3 am in school night, write it down, even if it's just as bullet points, cause sometimes the only thing stoping you from knowing what to write is your critical thinking, and that's kinda turned off when you're tired.