Yeah, the thing with Neville is that I do see his openly identifying himself with his failures as being a form of protection. What terrified him about Snape early on, I suspect, was that Snape never let him do that (that and he was mean to him). Neville, I think, probably has the attitude that he's admitted he can't do it, so leave him alone, but Snape just keeps trying to force him, which is a guarantee that Neville will do it wrong.

His grandmother is maybe similar, plus she's always telling him to be like his dad. She undercuts him, even not giving him his own wand. But Neville, in his quiet way, finds the things that interest him and that seems to be enough. Not to mention at times his family does seem to be genuinely supportive--they give good, appropriate gifts, the opposite of the Dursleys.