Much of this is taken from Digby's 'Symbol and Image in William Blake':
ALBION (Glad Day) was Blake's name for Everyman, Adam Kadman, Cosmic Man, the Eternal Great Humanity Divine (See Milton, plates 2 and 30) or in Quakereze 'that of God in Everyone'. Albion asleep is an apt commentary on Blake's age-- and ours.
"Every human life is part of Albion and can realize more or less the Cosmic Man's total nature... Albion suffers and triumphs in each individual, as is described in ...Jerusalem
..The Dance of Eternal Death" Digby p.12.
ETERNAL DEATH: Blake used this phrase 78 times; it's mortal life;I translate it to 'this vale of tears', the Sea of Time and Space from which we may emerge at the end; "whenever any Individual Rejects Error & Embraces Truth a Last Judgment passes upon that Individual.." [[A Vision of the Last Judgment] PAGE 85] (Erdman 562)
From Milton: In Heaven, having heard the Bard's Song,
"Milton said, I go to Eternal Death! The Nations still
Follow after the detestable Gods of Priam; in pomp
Of warlike selfhood, contradicting and blaspheming.
When will the Resurrection come; to deliver the sleeping body.."
JERUSALEM: This image cannot be defined; we can only begin a journey of 1000 miles. The Concordance has 288 occurences and Damon has 7 pages trying to describe it. Blake used it as the title for his largest poem; 'Jerusalem' the (smaller) poem, appears in the Preface to Milton (and in many hymnbooks): "till we have built Jerusalem in Englands green and pleasant land."
Jerusalem is the bride of Christ (the conventional church considers itself to be the bride of Christ, but to Blake the bride of Christ was the human race). Jerusalem was Albion's wife-- until he went to sleep; at that point he turned to Vala.
VALA is fallen Jerusalem. A picture is worth a thousand words, and the relationship betwem Vala and Jerusalem can be best understood in this plate (click on the pic for an enlargement). Jerusalem stands out in light with (supposedly) her three daughter, while Vala, in a dark vale, attempts to entice Jerusalem into her darkness. The two battle through The Four Zoas and Jerusalem (the large poem). In your life you can see the 'good girl' and 'bad girl' fighting for supremacy. A woman may become a thief, and/or she may give birth to a spiritual genius. Such is life.
Blake did not believe in 'good and bad'; he believed in Truth and Error. At the Last Judgment Error is burned up and we live (eternally) in Truth.