[He gets that feeling. Being worn down by your own power, it's such a pain, but that's just how it goes.

Childe hesitates, realizing that he'd been treating Falco more like an adult just now than the younger boy that he actually is. Perhaps that wasn't fair of him to do, and he regrets saying what he'd just said. Even though Falco has clearly taken on a great responsibility with his titan powers, though Childe has no way of knowing what that responsibility truly is, should he even be talking about killing around someone who is still so young?]

Falco...I apologize. I know you've been through a lot, but I shouldn't be making you face the truths of this world any faster than you already are. Let me put it this way- I was born to fight. So, I enjoy it in any form it comes in, that's all. It's as simple as that.

[That might be the best way of putting it before he goes off into a monologue about slaying powerful foes.]