"When at last I did descry the Immortal Man who cannot die, through evening shades I haste away to close the labors of my Day" (from Gates of Paradise).
It appears (to me at least) that no man has ever been more transparent in his life and works than William Blake. It seems that few of his many brilliant interpreters have come close to an overriding perception of Blake as a person; the one who may have come closest is Middleton Murry although his knowledge of Blake's work seemed relatively superficial.
Blake wandered through the Sea of Time and Space for forty years. To get along in this world was a sorry business for a man of his gifts of Intellect and Moral Fiber. He had a beautiful sunny side (evidenced by his Songs of Innocence), soon and often overridden by his caustic disappropation of the Culture he had to live in.
Life consists of contraries ("Without Contraries is no progression" MHH 3; E34). One of Blake's primary Contraries (and perhaps that of all Men of God) was the choice between following the Divine Vision-- or the 'Main Chance'.
In his letter 51 (Erdman 576) to William Hayley (2004) he told him (and us) that for ('exactly') twenty years he had followed the second one. Until at last [he] "descried the Immortal Man...."
That vision set him free from the tyranny of 'the Main Chance' and gave him some years of Creativity, which ended with a song on his lips. (Look at the last paragraph of Chap1.htm.)