The pattern calls for 4mm needles so I started with 3.75mm and the cuff looked huge. I ripped it out and started again with a smaller needle. I knit another cuff and a few centimetres of the pattern and realized it was going to be too tight. Rip! I went up a needle size and tried again, knitting the cuff and most of the pattern. It still was too small. Rip! Then I cast on using a 4mm needle. Much better. After knitting the cuff and a few more rows, I discovered I had made a major pattern mistake on the palm and ripped back to the row before. I used a 2.5mm needle to pick up the stitches and started knitting away again. A few rows later I realized I hadn't transferred the stitches back to the 4mm needle. Rip!
I now have finished the entire pattern and have begun a repeat to extend the hand long enough for mittens. I think I finally have it right. I'm calling them Stained Glass mittens.