I'm just going to take some themes offered by the commenters and suggest stuff, but just as an example-- could be entirely wrong for the story, etc. Standard disclaimers apply. No hard feelings, okay? :)
Let's take that "First impressions are deceptive." That's pretty simple and obvious. It's also the theme (one of the themes) of Austen's Pride and Prejudice. And I think it bears some relation to your theme above. But notice that it's not just the heroine who has a faulty first impression of the hero. He has a faulty first impression of her. And all through the story, there are examples of first impressions being right (everyone's first impression of Rev. Collins, that he's a self-righteous social climber, is correct), and long-derived impressions being wrong (Mr. Darcy's father is completely wrong to trust his protegee Lt. Wickham). So the simple "first impressions are wrong; long acquaintance impression is right" is not sufficient. Only by reading the entire book does the reader evolve the somewhat more nuanced theme that First impressions are deceptive. (They wouldn't be deceptive if they weren't sometimes true.)
And throughout the story, there are all sorts of contributors to the process of this theme. There's the main story (as someone says, "About a man who changes his manners, and a woman who changes her mind"), but there are other subplots and revelations that add to our growing understanding of first impressions. For example, the Jane-Bingley romance starts off shockingly well-- both of these pleasant people seem to fall in love quickly and readily. But as Jane learns, Bingley is too willing to believe that he was deceived by his first impression of her, and she herself must face the reality that this perfect young man has a terrible flaw-- in his eagerness not to be too gullible to her, he is too easily persuaded against her.
Even the reader might have a first impression that proves faulty. Mr. Bennett, Lizzie's father, at first seems charmingly wry, and her mother a monster of materialism. But (and not every reader will come to this conclusion!) through longer acquaintance, the Bennetts reveal themselves as more than their first impressions-- Mr. Bennett is a rather awful father, and Mrs. Bennett, for all her many faults, at least does care about providing for her many daughters.
And the theme which sounds so simple becomes increasingly complex as more complicated examples and developments emerge in the story. For example, Lizzie and Darcy actually benefit from their rash and negative opinion-formation, because they have nowhere to go but up in their mutual esteem. Jane, however, starts out adoring her Bingley, and can never quite again achieve that level of respect once he has proven himself less than worthy. BUT... he actually becomes more worthy when he starts to think for himself-- and what does he think? That his first, admiring impression was correct.
So-- I use that example because it seems that you're also working with initial impressions or attitudes. I hate to be reductive, but think about boiling your maybe too-individualized observation into something a little more general and universal. Not that you shouldn't individualize the STORY... but the theme is usually more open, more universal.
Next up when my hand is not so numb--