From the song "Sick Boy" by Chainsmokers, which quote or lyric would best go with the idea of struggling with self-identity?

I would argue that the following passage from this song deals most directly with self-identity:

Don't believe the narcissism When everyone projects and expects you to listen to 'em Make no mistake, I live in a prison That I built myself, it is my religion

The artists said in an interview that this song is largely about living up (or down) to a media-driven image unrelated to reality. These lines seem to directly refer to their struggles with self-image and that external, more artificial image. Like many celebrities, the Chainsmokers seem to feel that people "project" expectations on them and "expect" them to live up to or acknowledge them. Obviously, they are struggling with these expectations, and it seems to be, what they describe as a "prison" they "built" themselves through their work, which exposed them to this kind of attention. In fact, in the interview, they connect their own struggles with self-identity to that of their fans themselves, who, by putting their own images in the public through social media, are inviting the same kinds of criticism. As Drew Taggart, the songwriter, said in an interview:

I think about kids growing up with Instagram...they have their popularity statistics...and worrying about posting, and liking each other...and stuff that seems so meaningless is being taken more and more seriously now.

The passage above seems to capture this concern, both for a pop star and for ordinary people, fairly neatly.
https://www.forbes.com/sites/hughmcintyre/2018/02/07/the-chainsmokers-discuss-new-single-sick-boy-and-how-their-new-music-is-darker-than-ever-before/