The song is about a not so ideal situation that Brendon Urie really can't escape but he embraces it anyways. "I'm not a betting man but this is a sure thing" This lyric makes him seem that he doesn't plan the future but the experiences he did turn towards the bitersweet relationship.

"I've been to Tokyo and to South Africa
So many places that you may say I've seen it all
But my favorite place is the warm embrace
Of holding your hair back in a bathroom stall"

This is Urie saying how he exhausted his options saying "you may say I have seen it all" Some may argue that he can get out of a broken relationship but after all the adventuring he has done through he life Brendon argues that dealing with his hungover girlfriend is a good situation by his standards.

Hence the song name and the main chorus "Bittersweet" he compares the relationship to a sweet relationship that is also bitter, the two relationships are mutual enough where he can admit to loving the weird combination. and also of the chorus is saying "I guess that's how its gotta be" and "that were pulling teeth"

But he loves the relationship and he likes to talk about even though its supposed to be secret, which makes Brendon in this weird infatuation that makes him naive.I'm guessing he isn't used to this kind of relationship where he has to keep things in secrecy because he revealed he likes to talk, when he has an open person when the girl in the song is introverted and demurring most likely because of the abuse she lives with.