What is the overall tone of this excerpt from "when we two parted" by lord byron?

Read the excerpt from narrative of the life of frederick douglass. during this time, i succeeded in learning to read and write. in accomplishing this, i was compelled to resort to various stratagems. i had no regular teacher. my mistress, who had kindly commenced to instruct me, had, in compliance with the advice and direction of her husband, not only ceased to instruct, but had set her face against my being instructed by any one else. it is due, however, to my mistress to say of her, that she did not adopt this course of treatment immediately. she at first lacked the depravity indispensable to shutting me up in mental darkness. what sentence from the excerpt contains evidence of douglass’s misery at being denied an education? she at first lacked the depravity indispensable to shutting me up in mental darkness. during this time, i succeeded in learning to read and write. in accomplishing this, i was compelled to resort to various stratagems. it is due, however, to my mistress to say of her, that she did not adopt this course of treatment immediately.