[Arthur has to deliberate on whether he's going to be honest about this for a moment. The real answer feels a little crazy and he only managed to say it out loud once he got to Mal's and he doesn't want to burden Eames with this. It takes a little while before he speaks.]

Honestly, it's just the idea that I'm going to screw this up somehow. I mean, it's not like it's hard - vampires do it by accident all the time and you have to monumentally fuck part of it up to fail but... you're putting your life in my hands. Part of me really wants to delay that, which is why I'm...

[He gestures vaguely. He knows he's been pushing Eames to enjoy his time as a mortal, sometimes as a way to avoid talking about all of this, but now it's time.]