It's easy to not notice and leave out that last stitch on a row. I've had to take out many a row due to the same thing.
Some stitch patterns are easier to notice than others. I make sure I count stitches, every few rows, to make sure I'm not dropping stitches. Otherwise, it's discouraging and tedious to have to go back and do those rows over, especially a third time.

Hope you are making good progress now.