it was because she wouldnt have gotten over him
she would of said that she didnt care about her safety and that she just wantd to be with him

She freaks out whenever he mentions leaving "for her own good". if you'll remember, she nearly went mental when he said it to her in Twilight, when she was in the hospital in Phoenix. He knew she would go nuts if she thought that was the reason for his leaving, and thought for the sake of her sanity it was best for her to think he no longer loved her. Obviously he had no idea what the effect his leaving would have on her, because he didn't think she felt as strongly about him.

because he wanted her to think that he had moved on so that she can also move on! but if he had told her the truth she wldn't have let go! no that it worked but atleast he tried!

Bella doesn't bother about her safety. It doesn't matter to her, that it's dangerous or life-threatening. If he had told her, that he just leaves, 'cause he can't bear, that Bella isn't safe, she would've freaked out and there wouldn't have been the possibility, that she can forget him. When she knows, he loves her and leaves because of her, what do you think Bella would do? Let him go? Forget him? Or at least try to forget him?

He says he won't leave her but if he doesn't luv her anymore then he as no choice but 2 leave

a clean brake

She would not understand the reason!
And not let him go!
And, yes, the scene in the hospital is perfect too show what i'm talking about!

<3