Your instructor knows that your favorite/only time to work on your homework is late at night. If you have homework due the next morning and you start it at the last minute, you're just asking for frustration. Emailing your instructor and saying something like, "I don't understand this stuff. Can you extend the homework due date?" translates immediately to your instructor as you saying, "I am irresponsible and I wait until the last minute to do my work. Can you bail me out?"