close reading

Early on in my studies of English literature, I was never sure, when I had an idea about a poem - about what it meant or what the poet was trying to convey - whether I was right or wrong. But then, after a while, I realized that I could trust my ideas. 

That applies to anyone actually, and when I was tutoring I would tell students that. If you engage with the poem and you get something from it, that insight that you get is real and valid, more often than not. This is the case to varying extents, for all subjects, but especially for English because we each make our own meaning from literature or other kinds of text. In English, there isn't a right and wrong answer the way there is for maths and science. 

History too is malleable in that way. If you read and understand all the materials, and you're able to convey that understanding in your essays, you will do well even if your conclusion is questionable. That's why History essay questions will ask you about a particular issue and you could come down on either side and still do well, because what really matters is your ability to argue the side you choose.