What are expected swings due to variance? (and maybe a -little- help from me)

So this has been a ridiculous week in which I've been sodomized like new guy in a federal pound me in the ass prison. Which is leading me to wonder something about variance. I didn't really notice at the lower levels because it was so little money, and I ran pretty well how I should have as I moved up. But now I'm at the .10/.25, and had a very strong start, but now I'm getting butchered. I'm way plus EV on every street, but the river. I keep betting away while I have the best, typically half pot or so with each bet to deny odds on drawing boards, but the river somehow takes it all away with a miracle. I'm not above admitting I've helped the boning process, but analysis of my play says much of it is statistical rape. So now that I've ranted a bit the real question: What is a reasonable swing due to running like crap? People with a large sample size, what kinds of swings do you typically see when you've been staying on your game pretty well?