Ribbed Stitch is a Little Hard

I am probably the only knitter to have this much trouble with it.  But, the ribbed stitch is fairly difficult for me right now.  It's not that I don't get the premise, but for some reason, I keep knitting a purl or purling a knit somewhere, without even remembering I did it.  It's not a matter of identifying the stitches.  I totally notice when I look down and see it.  I think I've had to go back seven to ten times so far on this poor scarf.  I don't know if I'm just really inane or if this is common when you're learning to knit, what seems like a fairly straightforward stitch.