There have been many posts to this poem, which is so close to the words of Jesus' statement of the broad and narrow ways. He gave his full attention to the Spectre for 40 days (a full measure of time After 40 days the Spectre departed from him for a season. How long might that be??
The aforementioned preacher was conscious of the Spectre through the many years that he preached. Blake found it "around him night and day". He was a pretty good preacher himself, preaching to the church universal (VLJ N8I Erdman 559).
With 243 occurrences the Spectre dominated Blake's adult life for the first 20 years. That's evidenced by the pages and pages of accusations, denunciations and excoriations in his poetry. He stopped doing it like Los stopped fighting Urizen; once Urizen was in his power his hatred evaporated and he found he loved Urizen:
"Startled was Los he found his Enemy Urizen nowIt all boiled down to the admonition of Jesus to love our enemies. Who can do it? Only those who are "not of this world".
In his hands. he wonderd that he felt love & not
hate His whole soul loved him he beheld him an
infant" (4Z at the end of the seventh night)
In the same way he reconciled with the Spectre:
"But then the Spectre enterd Los's bosom Every
sigh & groan Of Enitharmon bore Urthonas Spectre
on its wings Obdurate Los felt Pity Enitharmon
told the tale Of Urthona. Los embracd the
Spectre first as a brother Then as another Self;
astonishd humanizing & in tears In Self
abasement Giving up his Domineering lust"
(4Z Erdman 367).
Los (Blake) stopped doing it when he saw himself loved (and called the 'ramhornd with gold'. The 'world' had lost its deathly grip on him.