Ok, I've known for awhile now, that I want to be a physicist however, since I've started reading online materials at a higher level, my grades have been suffering. I'm wondering if I've begun to over think things. For example studying heat we were told to "Ignore" some heat transfers taking place. Am I overthinking? And is there anyway I can continue to study higher level phyics and still get high grades? For reference, I am excelling in chemistry and biology and studying GCSE triple science and Astronomy. Also is there any material I should read prior to the start of GCSE Astronomy, to help me get high grades.