Dish rags

So I recently started knitting a dish rag. I'm working with size 7 needles and cotton yard. My last (and only) project I used size 15 needles, so these feel so tiny! They are as long as the size 15, but the size has to do with the diameter.

I'm working with a simple pattern, which makes a rib stitch basically.

By knitting one and then purling one across the row, you get these Vs.

The V pattern is called stockinette, which tends to curl, so you knit a few stitches at the beginning and end of the row, and the first few and last few rows to create a border. This also keeps it flat.

I started one, but somehow messed it up. I decided it was a good size and went to cast off. For some reason, when I knit the last few rows it gets very tight. While I was trying to cast off and I dropped a stitch, gah!

I did read on a few sites that when casting off, you should use a needle one size larger. Not sure why, but I am going to get some size 8 needles. It wasn't really a problem with the blanket I made, but maybe because it was size 15 needles and therefore bigger loops. I dunno.