What words does the poet repeat and what does it emphasize the differences between?

The repetition featured in Blake's poem relates to the process of repressing and holding in anger, as opposed to "coming clean" with one feels.  There are two parts to it:  When Blake speaks of confronting his friend and the anger with his enemy.  The latter is where most of the poem lies and where most of the repetition is featured. Naturally, as with all poetry, you are able to interpret the uses of repetition in any way you wish that links to the theme of the poem.  The poet uses repetition of words like "and" to emphasize the difference and complexity between confronting one's friend with anger and one's adversary with anger.  In the case of the former, it is a fairly direct process because of the relationship.  In the case of the latter, it is more complex because of the awkwardness of the situation and the repression involved.  In repressing our anger for sake of conventional notions of "politeness", we embark on a multipronged process of psychological damage and bitterness.  Intricate and manifold in its advancement of stages, the poet repeats the term "And" to highlight such development.