You've been so—[What's the word for it? Keith actually falls into silence as he struggles to find a way to adequately describe her behavior. Saying that she was acting like him wasn't right. Her behavior was far more mercurial than that. He was the pessimist. She was the optimist.

Emphasis on was.]

Look, you told me that because Luke failed, you'd go ahead and do what he couldn't do. But when we first met, when we started talking, you ... believed in people. You believed in me. It doesn't seem like you're doing a lot of that anymore. I just want to know why.

[It's not his way of saying "there's something wrong with you." Keith doesn't think that's it. He's just worried about whatever's driving her toward this reckless mindset, where she's acting this way.

He just doesn't really get that it can be interpreted as "there's something wrong with you," so whoops.]