I have completed more than six online courses in the last 3 years, and I have also worked as an editor at studyessay where we prepared our online course for students. And yes it is hard, especially when the course is complex and requires complete immersion.

I may say trivial things, but this does not negate their effectiveness. The first and most important rule is your interest and your motivation. They must be clear, you must know why and for what purpose you are taking the course. Next, you must assign a part of the day (e.g., morning) and the number of hours for learning. Try to be active and eat right, this will allow you to save energy for intellectual work. Good luck!