This sutra I want to write about is the sutra 2.46 Sthira Sukham Asanam. This sutra is answering to the question: What is asana? And the answer is: the posture is steady and comfortable. Sometimes is very easy to find both but many times we just ignore these two basic qualities. Why are they so important? well, at least for me, is because this makes the difference between yoga asana practice and exercise (any other disciplines where the movement of your body is involved). Yoga is about union and balance of the mind, body and breath. 
As you may have heard before, the image of the body is not important, what it matters is your experience through the practice, and this experience is the one that is trying to find steadiness and comfort. 
As beginners we will feel sometimes frustrated when not being able to touch our feet, or feeling stiff in hip, shoulders, or any other part; we struggle and often push ourselves beyond our body limits. Not only injuries happen, but the state of mind is reckless, is in discomfort, is noisy. I often see face expressions where you can tell they are clearly not enjoying the pose. Same happens with more experiences yogis, when we are carried away by our ego and desires to go deeper, to become better, to be more flexible and stronger. And while doing so, we fall in that same state almost contrary to what this sutra is talking about.
So my advice is at follows. Go where you feel your body is inviting you to go. It doesn’t mean there will be no effort, but you will know where to stop if you identify the quality of steadiness (you can stay for longer even though you feel the effort in your physical body ). And along with that action, comes to find pleasure in whatever sensation your body has. Find comfort in uncomfortable poses. Sometimes we easily label a sensation as pain, and the brain associates it with a negative experience. But if we follow the firs action of respecting our body to it’s proper limit, there shouldn’t be pain as an indicator of a possible injury; it may be only an unpleasant physical experience. So here is when the union of your body and mind is linked with the breath. The breathing will build the bridge between body and mind to work with a state of awareness and focus to in-body a pleasant attitude, pleasant mind. And because the mind is also a muscle, you can train your awareness to find steadiness in the flow and pleasure in the strength and effort. 
Speaking of mind, if we go deeper in the layers of the body, we will  also work with the mental and emotional body during practice. Thoughts and emotions arise while in some asanas, therefore, is important to be aware not only of the physical sensation, but also what lays underneath. 
Now, following a more truthful purpose of your practice, we should remember that the hatha asanas are meant to serve the body and prepare it for meditation. Let’s apply this sutra as well in our meditation practice. Finding steadiness and confort in your sitting pose; work with a steady and smooth breathing, maybe some pranayama like anulom vilom that will ease the rythm of breath; and these make it easier to enjoy a steady mind. 
OM TAT SAT