"I believe there isn't a god, though of course it's possible I could be wrong since nobody knows everything. I consider it pretty unlikely though, and I'm going to live my life as though there's no god until I see some decent evidence to the contrary."

And if you call it "agnostic", then how do you differentiate it from this position?:

"I have no idea what to think about the existence of a god: maybe there is, maybe there ain't. I expect we'll never know for sure."

Essentially, you're insisting that you don't really believe something if you admit even a faint possibility that you might be wrong. I hear this a lot, and I think it stems from failure to understand that in religions, unswerving belief is seen as a good thing, whereas for scientists it's a bad thing.