From the song "Sick Boy" by The Chainsmokers, which quote or lyric from the song would best go with the idea of struggling with self-identity (besides the quote "how many likes is my life worth")?

The entire song "Sick Boy" can be seen as the speaker questioning his self-identity and who he is. One of the most interesting lines that helps create that narrative is "Don't believe the narcissism / When everyone projects and expects you to listen to 'em."
When the speaker says "everyone projects," he's referring to the way we present ourselves to others. The culture in America is very focused on social media, and people don't put their true experiences on their profiles. Instead, they curate their content to present an image they want people to see. For example, a person having problems at work might focus on uploading happy pictures of outings with friends or images of their pets.
This leads to a struggle with self-identity for many people. They are forced to view their entire life against the best moments of everyone else's that are shared online. It's hard to feel like your life and self-identity are complete and measure up when you're comparing yourself to everyone else's highlight reel.
Another issue is that it's hard to develop a personal identity when you're attempting to project an image for others to like, comment on, and share. If the person you believe you are inside isn't interesting to those on a social media feed, you might tweak what you present in order to get more interactions with your followers. This leads to a curated personality instead of a genuine one.
When asked about the song, Andrew Taggart, one of the members of The Chainsmokers, talks about achieving fame. He says, "It felt a lot different than what we expected." For a lot of people, developing a sense of self-identity works the same way. You aren't necessarily the person you thought you'd be, and the experiences you have aren't necessarily going to feel how you thought they would. This is doubly true when you consider that the way you expect to feel about many things is formed, partially, by interacting with and viewing other people's experiences on social media.
In the same interview, Taggart says, "This song is kind of about discovering your self-identity while living in a world where everyone posts everything they do or projects kind of a curated reality on Instagram. And that's how we interact with one another." Everyone is interacting with everyone else's narcissism, and it's important to step away from that and develop your own sense of self. You're expected to engage with what people project on social media, but you have to focus on it less and focus on yourself more to create a real self-identity.
So, one of the strongest lines in the song to support the idea of self-identity is one that warns you away from influences that can keep you from developing your own. The Chainsmoker's label also commented on the meaning of the song and said that, in addition to self-identity, it's about "standing tall in the face of what you can and can’t control." That's a good reminder that you can't control what other people post, but you can control how you engage with it; stepping away from projected realities and choosing to ignore the narcissistic demands of social media can help a person develop a stronger sense of self-identity.
http://abcnewsradioonline.com/music-news/2018/1/17/the-chainsmokers-return-with-new-song-sick-boy.html

https://www.eonline.com/videos/268128/the-chainsmokers-share-sick-boy-song-s-meaning