"Why is it so hard to change my study habits?"

Article: We struggle to change our habits. Whether it's studying, lifestyle, health, whatever, we often KNOW what we want to do, but even though we DO want to do that, or know we NEED to change our habits, we just can't. How many times have you said "Next week, I'm going to study xxx way. I'm not going to procrastinate, I'm not going to take so long, I'm going to stick to my study plan etc?" So, why is it so hard to change our habits?