This has worked for me. Decide now on a chapter that you haven't reached yet as a goal. Force yourself to take a break when that milestone is reached and read

This has worked for me. Decide now on a chapter that you haven't reached yet as a goal. Force yourself to take a break when that milestone is reached and read something else in the intermission. If you still feel its worth the effort to finish the book, go back and pick up where you left off.