As you know, all teachers (and tutors!) were once students. So they know all the pitfalls that can cause a student to not get their homework done. The reason can be social - maybe the student wants to get his or her work done but the distraction of all the social media is too much to resist. The reason can also be academic - maybe the subject is difficult, such as challenging concepts or perhaps they're faced with an assignment that didn't get explained well enough to be done independently. Or sometimes it's the dreaded PROCRASTINATION. That can be the worst of all reasons to not get work done because the longer you procrastinate, the more the work piles up and then the student becomes "paralyzed", overwhelmed by the mountain of work that has accumulated.
When procrastination has gotten the better of you, the important thing is to not let yourself be so overwhelmed that you don't do the work at all. Here's what you do: PRIORITIZE AND GET STARTED! It is a simple phrase with a lot of impact. Look at the work that has piled up and then begin sorting it by due dates, difficulty, and so on. You would be surprised how helpful a teacher can be when he or she sees a student trying to get it together and do his or her best to catch up. Talk to your teacher/s, own up to the "slip" in not getting your work done, and see if anything can be worked out.
Of course, the important thing is to never get behind in your work. But honestly, sometimes it does happen. If you see the dreaded beast PROCRASTINATION making himself cozy in your work space, kick him out by prioritizing and getting started!