DISCLAIMER: I DON'T OWN TWILIGHT. IF I DO I WOULD BE IMMENSELY HAPPY....
When you realize that you very existence hurts over and over again the person that you love the most and that it might kill her; if you love that person as deep as you said, it isn't the right way leave and let her life her life without fear or any single trace of menace.
That's why I leave my dear love, my sweet angel, the reason of me very existence, my lovely Bella. I just wanted the best for her, to have a normal happy human live so, though this almost kill me I left her in pain but hopping she'll be up again soon.
And of course, when I know that she was dead, it was the end of my world, my life, because even though I've already say goodbye to her I could live knowing she was alive; and also know that when she was definitely gone from this world I will follow her and maybe then we finally can be together.
So, here I was, about to give up my life and hopping whit all my whole being that I have a soul so I can be with her.