Well, the Autobiography of Frederick Douglass is a very well regarded and beautifully written account of his upbringing and enslavement. Though I'm not sure which edition is best or if it matters. There's lots of stuff about its effect on his mind, the intense will power he had to exert in order to preserve his spirit, described in very vivid language. Of course, as far as historical sources go you should give it the due caution that any memoir deserves. People are rarely completely accurate when describing themselves and their actions and their motivations. But it is certainly a valuable source for the kind of perspective you say you're looking for.