Why do I constantly push myself?

I have been doing homework since noon. Why? Because I told myself that I would. I have this book to read by Friday. It's 59 chapters and we have to take notes on every chapter. I always set a goal when I read because I feel like it's easier to get it done. So I set my goal for page xx, but when I meet that goal I don't feel like it's enough so I set a new one for page xxx. WHY!?! You would think that I would be satisfied with meeting the first goal, but hell no. I push myself. I hate that about me. The book is so unbelievably boring and I don't push myself because I enjoy reading or because I find the book interesting. I don't know why I do it. If I didn't meet the second goal I would feel like such a failure! I wish that I could be satisfied, but I am not and I probably will never be because I have been doing these same things since I could walk. Maybe things like this have put me where I am in life, which is a good place to be, but it still bothers me. I have high goals for myself and I know that I am capable of everything that I set my mind to and that every single goal of mine will be met, but I am killing myself while doing this. It just eats at me and eats at me. Me and my "goals" is why I am so stressed and exhausted. My next, much-needed counselling session is Tuesday. We are slowly finding out that I tend to have more panic attacks and stress towards the end of the week.