Maybe I'm missing something.

I'm not saying my behavior is random, or un-caused. I experience preferences among actions. Factors I'm unaware of undoubtedly play a part, something I can speculate on, and others as well, and I or they could try to model them. But as I experience reality, I'm only striving up to a point to do the Right Thing. My speculation is that if the cost exceeds the cost of reminding myself I'm actually a nihilist, I'll bail on morality.

I'm very interested in arguments as to why nihilism isn't a consistent position -- heck, even why it's not a good idea or how other people have gotten around it.