I could see it being a bit of both. Lyrics are often inspired by something and describing something else. In this case, someone stalking a former lover could be seen as “going full 1984’s Big Brother” on them… and it makes sense with the whole romantic mood that the song has: the stalker sees themself as romantic and sings it that way, but when you look closer you realise it’s actually very creepy.

Don’t look into the story behind “My Sharona” by The Knack.

Doesn’t it say “I get up and nothing gets me down”? I always thought that sentence described being motivated and not letting anyone ruin your good mood.

Do you maybe mean “Every Breath You Take” by The Police? That’s a common answer to this kind of question. A lot of people think of it as cute and romantic at first, but the song really talk about the Big Brother (from George Orwell’s 1984): a state of constant surveillance watching “every breath you take, every move you make”.