How we cite our quotes:
"Why is that," my voice shook, embarrassing me, "do you think?"
I felt the tremor of this breath on my neck as [Edward] laughed. "Mind over matter." (14.165-6)
Edward hopes his mind can control what his natural instincts tell him to do.
[Edward to Bella :] "That's a good question, and you are not the first one to ask it. The others – the majority of our kind who are quite content with our lot – they, too, wonder at how we live. But you see, just because we've been…dealt a certain hand…it doesn't mean that we can't choose to rise above – to conquer the boundaries of a destiny that none of us wanted. To try to retain whatever essential humanity we can." (14.231)
Most vampires do not fight fate. They follow their natural instincts and feed on humans. The Cullens, however, make the conscious choice not to harm humans. It's hard, but in return for their sacrifices, they have clear consciences.
[Edward to Bella:] "Carlisle knew what his father would do. The bodies would be burned – anything infected by the monster must be destroyed. Carlisle acted instinctively to save his own life." (15.247)
After Carlisle became a vampire, his fate was set. His family would hate what he'd become and kill him – they'd see no other choice.