Are you talking to me? I love that scene. I have no issue with the "death by broken heart"--I find it (and the accompanying self-fulfilling prophecy) to be the most mature writing in all 6 movies. No, Luke wasn't trying to convince himself--Luke felt he was right, and turned out to be right. The reason why I feel that Padme is trying to convince herself and failing is that expressing a glimmer of hope while dying of a broken heart is a bit inconsistent with the trope. It doesn't bother me, as I understand why that line is there. But making the assumption that Padme fails to convince herself removes that (slight) inconsistency. I love @JediGirl_Angelina 's notion mentioned above, that Luke's conviction is based on a Force memory of Padme saying that. Very neat idea.