This is a good principal for all areas of life, whether you're tackling homework, chores or your to do list. If you put off the hard things you will most likely run out of motivation and possibly time. If you do the hard things first, you will be more likely to have the motivation to keep going through the easier tasks too. Plus you will have the satisfaction of crossing them off your list, rather than the nagging dread that they still need to be done.