I was taking a philosophy class, which met twice weekly. Assignments for each class consisted of reading select passages from different philosophical works. In addition to the selected passages, our teacher provided recommended secondary literature/commentaries to help navigate the texts and provide different perspectives.
In regards to the readings, due to various (mostly health-related) reasons, I often fell behind. This, for the most part, was not an issue, as the essay assignments for the class concerned very specific sections of the texts. In writing these, then, what I would do was consult both online summaries of the relevant sections and peruse the relevant sections from the texts myself.
Come the final exam (for which we were provided the questions ahead of time), while I was initially concerned that my having fallen behind would hurt me, it turned out that most of the questions I could answer based on what I already knew. As I was preparing for the final question, however, I realized that I needed to really understand one section of a book that I hadn't read; this was the night before the exam. This section was really dense, so while I tried for a time, and got partway through it, I decided it would be more prudent to consult one of the recommended commentaries in order to understand what the philosopher was saying. While I was doing this, I tried a few more times to make it through the actual text again, but I didn't get that much further. The secondary sources clarified the argument the philosopher was making, and I used what I'd learnt to finish my answer. Ultimately, the information I'd gleaned from the secondary source took up only a small part of my final answer.
At the time, I felt a pang that maybe I was doing something unscrupulous, and thus that I should just rely solely on the primary text. Would it be wrong, I asked myself, to rely predominately on the secondary text given my minimal understanding of the primary text? But I also knew that I had somewhat of a history of compulsive, irrational guilt which had affected my performance in the past, and thus I was more determined not to let this hurt my performance on the exam, so I did end up using the secondary source.
After the exam, I later informed the teacher that in preparing for the final, I had consulted online/secondary sources that provided some information/ideas which I hadn't taken from the text, and he replied that this was completely fine. I realized, however, that I hadn't said specifically that I hadn't made it through the relevant section completely and with trying to understand it fully, and that maybe I should've actually clarified this as well.
The crux of my dilemma, then, is to what extent I should have read/comprehended the original text before relying on secondary texts/summaries. Generally speaking, throughout the course, while I relied a lot on secondary sources/summaries, I made efforts to read the actual texts as well. For the final, however, I tried to read the actual texts, and did to an extent, but understood it only superficially, and ultimately the bulk of my understanding came from the secondary texts/summaries. Moreover, as I was reading the primary text, I felt a bit that I was only doing it so that I could subsequently turn to the secondary text without reservations—i.e., without relying on the secondary text entirely without having read the primary text at all. It's worth noting as well that the secondary source I consulted predominately in answering this question was recommended by the teacher, and to my knowledge it was never stated explicitly that we could only use secondary commentaries after having read the primary texts.
I'm wondering whether I should feel bad about this going forward. I've come to the conclusion that, while at worst this may have been a minor infraction, it isn't worth feeling bad about and I shouldn't let this hang over me at all going forward, nor should I attempt to further clarify this situation with my teacher, especially given that the class is over.