I think this song means telling someone you're feelings about them before time runs out. You should love them like you're gonna lose them. Tell them what they mean to you - and hopefully it's something nice ;) - and hope for the same thing back. Spend as much as time with your loved ones as possible. Because you never know when something might happen and time will run out for either one or the both of you.

To me, its about the good ol' days when the boys were just Luke Hemmings, Calum Hood, Ashton Irwin, and Michael Clifford. Not Luke Hemmings, Calum Hood, Ashton Irwin, and Michael Clifford from 5 Seconds of Summer. "I drove by all the places we used to hang out getting wasted." They can't do that anymore, they are always busy and exhausted. "I wish that I could wake up with amnesia and forget about the stupid little things." Everything might just be too much for them and they might just want their old lives back. Everything as in the fans, the concerts, management, the hate, the constant paparazzi following them all over the world in every dark corner, every alleyway, every exit. "The pictures that you sent me they're still living in my phone. I'll admit I like to see them, I'll admit I feel alone." They still have pictures from when they were normal teenage boys hanging out with their friends. They like to occasionally look at them for old times' sake, but feel this empty hollowness in their hearts. That empty hollowness is called longing. They long to go back in time and relive those special moments. But it could also be a break up song. In one of their concerts, Calum mentions that this song is about a girl named Amnesia. Not about waking up with the illness amnesia, but with a girl. It all makes sense either way. Hope this helped with whatever you were looking for!