This may sound weird, but I always feel really guilty for writing anything that isn't my novellas when they aren't done yet.
Even more so if the deadline is coming up.
Yesterday I ended up writing 6000 words that was unrelated to my novella, and it felt like I was using the time I should have been working to write something only for me.
It's foolish, I know, but I guess it's part of how my brain is weird. Even more so now that I kind of only have thirteen days to finish the current novella that I'm working on.