It took everything...

Edward: It took everything I had not to jump up in the middle of that class full of children and-- When you walked past me, I could have ruined everything Carlisle has built for us, right then and there. If I hadn’t been denying my thirst for the last, well, too many years, I wouldn’t have been able to stop myself. (pause) You must have thought I was possessed.
Bella: I couldn’t understand why. How you could hate me so quickly...
Edward: To me, it was like you were some kind of demon, summoned straight from my own personal hell to ruin me. The fragrance coming off your skin... I thought it would make me deranged that first day. In that one hour, I thought of a hundred different ways to lure you from the room with me, to get you alone. And I fought them each back, thinking of my family, what I could do to them. I had to run out, to get away before I could speak the words that would make you follow.... (pause) You would have come.
Bella: Without a doubt.
Edward: And then, as I tried to rearrange my schedule in a pointless attempt to avoid you, you were there-- in that close, warm little room, the scent was maddening. I so very nearly took you then. There was only one other frail human there-- so easily dealt with. But to resisted. I don’t know how. I forced myself not to wait for you, to follow you from the school. It was easier outside, when I couldn’t smell you anymore, to think clearly, to make the right decision. I left the others near home-- I was too ashamed to tell them how weak I was, they only knew something was very wrong-- and then I went straight to Carlisle, at the hospital, to tell him I was leaving. I traded cars with him-- he had a full tank of gas and I didn’t want to stop. I didn’t dare go home, to face Esme. She wouldn’t have let me go without a scene. She would have tried to convince me that it wasn’t necessary... By the next morning I was in Alaska. I spent two days there, with some old acquaintances... but I was homesick. I hated knowing I’d upset Esme, and the rest of them, my adopted family. In the pure air of the mountains it was hard to believe you were so irresistible. I convinced myself it was weak to run away. I’d dealt with temptation before, not of this magnitude, not even close, but I was strong. Who were you, an insignificant little girl, to chase me from the place I wanted to be? So I came back... I took precautions, hunting, feeding more than usual before seeing you again. I was sure that I was strong enough to treat you like any other human. I was arrogant about it. It was unquestionably a complication that I couldn’t simply read your thoughts to know what your reaction was to me. I wasn’t used to having to go to such circuitous measures, listening to your words in Jessica’s mind... her mind isn’t very original, and it was annoying to have to stoop to that. And then I couldn’t know if you really meant what you said. It was all extremely irritating. I wanted you to forget my behavior that first day, if possible, so I tried to talk with you like I could with any person. I was eager actually, hoping to decipher some of your thoughts. But you were to interesting, I found myself caught up in your expressions... and every now and then you would stir the air with your hand or your hair, and the scent would stun me again... 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.’
Bella: In the hospital?
Edward: I was appalled. I couldn’t believe I had put us in danger after all, put myself in your power-- you of all people. As if I needed another motive to kill you. But it had the opposite effect. I fought with Rosalie, Emmett, and Jasper when they suggested now was the time... the worst fight we’ve ever had. Carlisle sided with me, and Alice. Esme told me to do whatever I had to in order to stay. All that next day I eavesdropped on the minds of everyone you spoke to, shocked that you kept your word. I didn’t understand you at all. But I knew that I couldn’t become more involved with you. I did my very best to stay as far from you as possible. And every day the perfume of your skin, your breath, your hair... it hit me as hard as the very first day. And for all that, I’d have fared better if I had exposed us all at that first moment, than if now, here-- with no witnesses and nothing to stop me-- I were to hurt you.

~Twilight, Stephenie Meyer