Rabbi Yaakov Emden was one of the first, and one of the few, to write an intimate autobiography which focused not only on his life events but also his emotions (a very 18th century thing to do).
He was the son of Rabbi Tzvi Ashkenazi, and followed in his father’s footsteps in the quest to eradicate Sabbateanism. He fatefully accused Rabbi Yonatan Eybeschutz of being a closet Sabbatean, kicking off a controversy that divided Europe.
He complained about depression and lived a sad and miserable life. He wrote dozens of books on a wide range of topics, in both halakha and theology.