Ask HN: Have my fears been confirmed?

I have always doubted whether I would be a successful programmer; in high school I excelled in history and politics. I pursued a BA, not a BS, in CS in college, and am doing reasonably well because of my effort. I have had some rough spots where I considered changing majors, but stuck with it, and learned some c,java,python, and sql in the process. I doubt my own skills not because two months ago I started my Internship, and I messed it up terribly. The first two weeks I was not given a lot of work because my team was already in the middle of a huge project. My mentor told me to read the code. I did, but was slow to start, because I did not know where to begin, and slow to understand. By 3 weeks, I understood some of what junit tests and what spring was, two concepts heavily used in the code base, but could not really contribute. However, I would volunteer for a few little tasks each week. I also had a horrible habit of sleeping late, so I would show up to work tired and unmotivated. I told myself that I was reading the code, but really I round be distracted on my phone, ensnared in theology and history books. My manager was so stressed that I could get away with this. So I was listless and useless for a few weeks. Towards the end, my manager gave me two small projects, and I did each, although I was not good with keeping tabs with him each day. When I finished each, I wanted to show him, but he was not interested. I learned today that during this weeks where I would lazily “read code,” he was expecting me to take initiative and come up with ideas. I also should have not kept sleeping late. I just blew a six figure job away. I feel stupid and entitled (why was I so sure I would get a return offer?), but now feel the need for personal discipline and to really start coding and reading coding books in my free time. I sort of dislike school thoug, and am afraid, with my BA, that I blew my lucky break