"No Changes" are tough to swallow. I remember when I tested for my blue belt in Karate (equivalent=yellow belt in Taekwondo) many years ago. The news came as a shock and it was hard to come back to class wearing the same rank while my classmates had moved on. My instructor took me aside and explained why I was not promoted and what I would need to show before I could continue. She worked with me on chambering and re-chambering my front kicks, which are some of the finer details expected of the 2nd rank in the style. After a few classes of training, I took a make-up exam and was promoted to blue belt.
From this experience, I learned to expect more from myself and how to practice while performing self-evaluation using a mirror.