Complex sentence: Sabini & Silver argued that postponement and irrationality are the two key features of procrastination; putting a task off is not procrastination, they argue, if there are rational reasons for doing so.
Split into simpler sentences: Sabini & Silver argued that postponement and irrationality are the two key features of procrastination. Putting a task off is not procrastination, they argue, if there are rational reasons for doing so.