This relates to the theme, because, this poem expressed how someone can change into someone they aren't. 
Reading that helped me understand the theme better by showing how someone can regret their change that they made. Something changed the writer, because it stated, "It has changed me" and  "It has transformed me". It used the word "it" as in something besides his or her self. 
The person who wrote this or who about probably changed for something besides their own good and covered the old them up. Whatever changed him or her, the person no longer likes the change. 

Situation Change: Stability and Change of Situation Variables between and within Persons

Rauthmann et al. ( 2015b) clarified that there are different phenomena that have been referred to as "the situation" in extant theory and research: situation, episode, environment, and context. These terms are hierarchically nested within each other. Several situations (e.g., being greeted by friends, getting something to drink, listening to loud music, a vivid conversation, etc.)

pubmed central (pmc)

What the topic was meaning to say was that when someone goes through something awful in their life, like certain problems they face, the person can sometimes change the way they act or respond to things. A person sometimes changes to please others or themselves if they don't like something about themselves. When a person changes, they bury something deep down with themselves to sometimes cover up the old them or to hide their true selves. People tend to change, because they sometimes feel like they have to fit in with society. Certain things or situations can cause someone to change, sometimes change can be good.