Blake spent his youth denouncing the 'Enemy': an oppressive political and economic conspiracy against Albion--its tool, the 'State Church' (all churches in fact), exploitation of the poor, the Art merchants who approved only commercial art (they had dealt with Blake like the Pharisees dealt with Jesus), and finally the misguided help of a 'corporeal friend'.
Jerusalem, Plate 76
After all this came the Moment when he heard the voice: "thou ram horn'd with gold", and he knew himself accepted and used by the Eternal Powers that abide after all the above has passed away. Here's where he was at that point in his journey through life, and the system with which he reported it.
He came to see that the 'Enemy' was within (we have met the enemy, and he is Us). He 'came to himself', he confessed his sins. Henceforth the annihilation of his selfhood (Jerusalem, Plate 5, line 23) and the power of Forgiveness became his chief motifs. The old, old story was told again.