How we cite our quotes:
I'd never given much though to how I would die – though I'd had reason enough in the last few months – but even if I had, I would not have imagined it like this. (Preface.1)
Bella is facing her death. Interestingly, despite Edward constantly warning her that she's in danger, Bella thinks about her own mortality for the first time when she faces James.
When life offers you a dream so far beyond any of your expectations, it's not reasonable to grieve when it comes to an end. (Preface.4)
Bella thinks that her life has been amazing and is grateful for what fate brought her. She seems to be saying that meeting and spending some time with Edward was an experience worth dying for. She wouldn't trade it for anything.
[Edward to Bella:] "Of course, then you were nearly crushed to death in front of my eyes. Later I thought of a perfectly good excuse for why I acted at that moment – because if I hadn't saved you, if your blood had been spilled there in front of me, I don't think I could have stopped myself from exposing us for what we are. But I only thought of that excuse later. At the time, all I could think was, 'Not her.'" (13.117)
Edward speaks of how he felt when Bella had one of her brushes with death. He already had an instinct to protect her at all costs.