Songfacts®:

• This song is about NOFX frontman Fat Mike's 2016 trip to rehab to kick an opioid addiction, which he documented on Instagram. Mike entered a program run by Noah Levine, a Buddhist punk rocker with a spiritual approach to recovery. It went really well until day six, when he felt the full force of the withdrawal.
  
  Mike had been dealing with a Valium dependency for years, and at one point it almost fractured the band - drummer Erik Sandin ("Smelly") was a recovering heroin addict and had a hard time watching Mike indulge his habit.
• This is an example of a NOFX song that most people won't understand but will really connect with those who do. "People don't know what 'F--k Day Six' means unless you were addicted to opiates, because day six is when it really hits you," Fat Mike told Songfacts. "Only 10% of the listeners will understand. But that's what I like, is for some people to really relate to a song. If you write a song that everyone can relate to, that's not fun for me."
• NOFX released this song on Double Album, which is really a single album, but can become a double album when combined with their previous release, Single Album.