Honestly, I don't like this #amwriting advice. I feel like a lot of people get told it and then they get it stuck in their head that their first line must be this uber unique, uber compelling thing and you open a book and that first line feels like it's trying so hard when what makes a really compelling line in most cases is something that's true to the character. Maybe if you're writing poetry or poetry prose it matters more, but starting with some obscure line that doesn't relate so much to the character or action just to have that 'money shot' of a first-line... is silly... and heeps on a bunch of pressure to "get it right immediately" it feels like. Should the opening of your novel be compelling? Definitely. But compelling doesn't mean super incredible, uber unique lines. It means character, characterization, setting, stake... honesty IMO.