Hayley strongly discouraged Blakes 'indulgence' in 'Visions' and more or less insisted that Blake spend his time "making Designs & little pictures (miniatures) with now and then an Engraving". This is the way Blake could make a living, Hayley felt.
But making a living was not Blake's priority, nor is it for any poet worthy of the name. His top priority was to follow his conscience. So Hayley had introduced a conflict in Blake's life (it had been there all along, as it is in any poet, a conflict between income and calling--"no man can serve two masters"). Hayley precipitated the crisis: either live like a respectable middle class person or follow God's call (as he understood it).
Thank God he made the right decision. To it we owe Milton, Jerusalem, Illustrations to the Book of Job and some other exquisite works, especially pictures (in his last years Blake leaned toward painting over poetry).
The letters in the post (Blake's Crisis) address the conflict and also reflect its resolution. In the first one, Letter 10, to a less demanding patron and sponsor, Blake tried to explain to Cumberland the cause of his "stupid Melancholy"; he felt compelled to do things that were against his best judgement.
The second one, Letter 24, was to his truest friend (actually his confessor); he told Butts that he had found "great objections to my doing anything but the meer drudgery of business" (on the part of Hayley, no doubt).
The crisis had been resolved when Blake, now back in London, wrote Letter 51 (almost two years later) to Hayley. In the meantime Blake had expelled a drunken soldier from his garden; the man charged him with sedition and other capital offenses; Hayley went to great length to get the best possible legal defense for his friend, and Blake was acquitted. Under those circumstances you can imagine how his attitude toward Hayley changed.
Later evidence indicates that Blake thereafter went out of his way to be of assistance to Hayley, who had "domineered over me, he is even as a brother who was my enemy." He apparently had the freedom to confess to Hayley that he had felt 'domineered' during the Felpham years.
It's interesting to speculate whether the Spectre poem in which Blake wrote,
"Let us agree to give up Love
And root up the infernal grove
Then shall we return & see
The worlds of happy Eternity
& Throughout all Eternity t
I forgive you you forgive me
As our dear Redeemer said
This the Wine & this the Bread"
was written before or after Blake's experience with Hayley.