Vic Fuentes writes most Pierce the Veil
songs by taking raw personal experience and transforming it into poetic, indirect lyrics. Even though they're drawn from his life, the finished song is often left with an ambiguous, universal feel. This is partly intentional, as Vic admits that he will censor and rewrite lyrics if they deal too explicitly with a real person. This was the case with "One Hundred Sleepless Nights", which is based on Vic's on-again, off-again relationship with a woman over the course of several years. As the two were finally reconciling and moving toward something that felt permanent, she got pregnant with another man's child and moved away. The song describes the night that Vic found this out.
The song, despite being rewritten to avoid directly referencing the woman involved, is lyrically straightforward for Vic. From start to finish, it simply describes the woman showing up and telling Vic she's having another man's child. Vic's characteristic poetic stylings, however, manage to show up between verses, as he imaginatively describes the savage emotions provoked by the experience. Vic says that this is the most personal song for him on the album.