Diamond blanket instead of square

I just completed a diagonal baby blanket and it came out looking more like a diamond than a square. What did I do wrong?? I followed the pattern which is similar to the basic dishcloth pattern. Can anyone help me out. Thanks!

[size=2]edit - [color=violet]mod squad was here[/color][/size]

One possibility is that your row gauge was larger than that of the pattern or your stitch gauge was tighter in proportion to your row gauge. I honestly don’t know of a way that you could do it differently, though.

My diagonal washcloths tend to do that, too. Once they are washed they seem to fine so give that a try if you used washable yarn.

It may be from the bias nature of the blanket. When you cut fabric on the bias, it stretches more in one direction than in the other. The same is often true in knitting.