The speaker of the poem tells of his visit to the Garden of Love and of the chapel that is now where he used to play as a child. Instead of welcoming him in, the chapel has ‘Thou shalt not’ of the Ten Commandments written over the door. The speaker sees that this negative morality has destroyed the garden as well, transforming the ‘sweet flowers’ to graves and tombstones. The emotionless ritual of the priests ‘walking their rounds’ threatens to choke out the speaker’s life itself.  The secret to the poem lies in its second line.
The speaker is talking about the change in how he now sees his surroundings, not a change in the garden itself. The poem marks the psychological passage from childhood innocence to adult experience. There are strong elements of the passage from innocence to wisdom of Adam and Eve in the Garden of Eden. Just as the biting of the apple interpreted as a sexual awakening, so is the speakers ‘joys and desires’ include the pleasures he is denied by the rules of morality set by the church. The gates of the chapel being shut symbolizes the fact that the church was separated from common society and tried to exclude the individual from building a relationship with God and gaining a personal understanding of God. The church was constantly telling society what they were not supposed to do and trying to dictate every aspect of their lives, which took joy out of many things in life.
This further separated man from God. The last two lines, with their meter and rhyme pattern, sum up what Blake saw as the threat of losing the ‘joys and desires’ of childhood innocence: unless we can develop our creative imagination to replace that lost innocence, we will lose the essence of life itself.