Teaching becomes part of your yoga practice, but your dedicated practice does not guarantee you will be a good teacher!
I think periodically about the adage "Those who can, do, and those who can't, teach," and how it applies, or doesn't, to yoga. To have a yoga career, you will have to teach. But nobody can teach yoga well without also 'doing,' as our own practice informs our teaching so much.
I often get the question from new teachers: "Do I have to be able to do a handstand to teach it? Do I have to be able to do an arm balance to teach it?" And my answer is, more or less, "sort of".
You have to have some relationship with the pose to be able to teach it, but this does not mean you have to have reached a penultimate variation of the posture before you can safely lead others toward it. You do have to have sensed into your body what's involved to gravitate toward that pose. You may even need to have struggled with it. You should struggle with it. You should question why you can't do it, you should try to do what you can toward it, and you should study what you are doing on days when you get closer toward it.
All of this will help you teach a pose, even if your leg does not go completely behind your head.
Being an excellent teacher does not require having the most advanced practice in the room. Having the most advanced practice in the room does not guarantee you will be an excellent teacher.
When we practice, we can go deeply in, and guide ourselves from sensation without a need for verbalization. To teach, you must be able to translate that sensed experience into words that make sense to other people.
I have two degrees in writing. I studied the English language, and poetry, for my entire academic career. Yoga was my practice on the side. Over time all of my written work became about the body, and the merging of my passions was clear. I love teaching yoga because I am writing poems the whole time I teach. I am putting to work all of my training as a writer every time I show up in the studio.
Teaching feels like this to me: First, I have to closely observe myself and my students, and then I try to joyfully meet the challenge of verbalizing what needs to happen to create pose progress and refinement. Honestly, I love it.
I love working on hard poses, by myself or with my teachers. And I love when I crest a new asana-mountain top and catch a view I haven't seen before. This is not completely unrelated, but also certainly not the same, as my teaching practice.
When I show up to teach / When I show up to practice. Both occasions require just that: showing up. In an awake, aware way. Both stir the pot of 'practice' for me, activating my attentions so that I grow through both experiences. But, they require a different skill set.
When I lead teacher training programs, this is one primary goal: train new teachers to develop the skills of clear communication. Teach them how to understand what is actually happening in their bodies when they practice, and how to put this experience into understood language. Honestly, I love this too.
Further your practice; further your teaching. Pay attention...to your body, and to your words.