The main theme in this poem would probably be anger, as it is expressed throughout the poem. The poem begins off with being angry at his friend “I was angry with my friend” and being angry at his enemy “I was angry with my foe”, making the reader identify to the fact anger is portrayed and, more importantly, some of the destructive consequences that can result when we hold our anger within us, rather than trying a more productive solution for this potentially dangerous emotion in which we tend to use to strike other people. The fact that Blake refers to anger as "wrath" suggests that the poem is about a more serious type of anger which could be either spiteful or vengeful. Now the speaker of the poem reveals to his friend that he is angry, and the anger dissipates “I told my wrath, my wrath did end”, but when the speaker hides his anger from his enemy, the anger grows, much like a tree “I told it not, my wrath did grow”, thus giving the name “Poisonous tree”. The lesson to be taught is that if we don’t relieve our anger by communicating without the use of violence, then we cannot dissipate our anger, as it will only grow more and more. If we ignore or deny our feelings, we will become harsh, cruel and perhaps even vengeful.
Opinion: I’ve had similar experiences myself, but with friends usually rather than enemies. Gossip is what got to me, as I used to talk trash behind people’s back just because I hated them for some odd