Do I Look Like a Protagonist? Ways to Describe Your First Person Narrator

I just came across this blogpost on how to describe a narrator in a first-person story. I now am asking myself if I am going against what is said here:

Avoid the Mirror Trick

It seems like an easy answer to simply have the character look in a mirror and describe what they see, but it’s been done so many times (and done badly) that agents and readers cringe when they see it. If the novel happens to start this way, it’s likely a kiss of death unless there's a unique twist to it. 

Avoid the “Let Me Introduce Myself” Cliché 

Another common cliché is having the character introduce themselves and describe what they look like. For example, “I’m your average gal, five foot four, brown hair, blue eyes” or “I’m nothing special, six foot, black cropped hair and brown almond eyes.” This was quite popular a while back, but these days, it usually comes across feeling stale.

Here is part of one of the opening paragraphs from my story (which I have quoted on my blog previously):

... I hate the way I look. Curly dark hair, dull-looking brown eyes and teeth sticking out in all directions…an overbite. It should come as no surprise that my dentist said I need braces. ...

Does this appear to doing what the post says not to do? I know that no rules are hard-and-fast, but I still want to to see what others think. Those who've read my manuscript or have seen quotes from my story on my blog will know that the character's teeth are important to the story since it revolves around him getting braces. Those who have read my story will also know it is a diary-style format. I now wonder how the "mirror trick" or "let me introduce myself" cliché applies in this instance. Again, nothing is wrong or right about this, but some things, like these, are good to know to help in policing your work.

How many of you have had this happen in your work?