Okay but Bellamy refused to accept the possibility that Clarke was actually going to die. He would not hear it, and he listened to her ‘if something happens to me’ speech because she said she needed him to, but he pushed away the idea that Abby’s premonition had any merit right up until it was too late and they had to leave without Clarke.
He is going to feel so guilty for that. He’ll think that if only he had listened, he could have done something - maybe he could have climbed the tower instead, and the whole chain of events would have turned out differently. Maybe Murphy could have rescued Monty by himself, and he could have stayed to help Clarke somehow. None of these options really make any sense, but he’ll torture himself with the idea that if he’d just taken Abby’s premonition and Clarke’s dread seriously, he might have been able to do… something.
Not only that, but Clarke told him what she needed to because she had accepted that she might not come out of this alive. Bellamy was shutting that whole realm of possibility down in his brain, so he didn’t take that opportunity. He never finished his sentence from 4x06 - ‘If I don’t see you again’.
He just wasn’t finished.