Why I Rarely Do Not Finish a Book

I have a hard time giving up on a book. Like I can totally hate it and the book can be boring me like crazy, but I have to finish this book. I am an optimist and sadly I feel that even the worst book ever will at least have a quote or something that will make all of the time that I spent is worth it. For some books, I am angry at myself for not being able to quit a book. The only time that I have been able to do it was for Cybils and that was still extremely difficult to quit at 50 pages.
I think that part of the reason is that my mom is the same way. One time, we were talking about a book that she was reading and I hated it. My mom ended up hating the book, but she still finished it. I guess it might just be the need to know if I am right or not. I think that another reason is I am always guessing if the book is predictable or not and I really like when I am right. I can also not quit series, there are only one or two that I have started that I plan to never finish.
A lot of the time that I am reading isn't at home, it is in between classes, at the doctors, at the gym and on the bus. If I decide to give up on this book, I won't have anything to read until I get home, which could be hours later and in that time, I could just read the book. Anyways, I was wondering if anyone else has this issue or if you are able to quit easily.