Here is one thing I have learned in my years of teaching and yoga practice: If you keep giving yourself steady doses of the basic poses, your competency in the more advanced poses will also develop.
I like to think of it as filling an ice cube tray. Sure you can pour water into each individual cube space, but you can also just tilt the tray and let the water cascade from the top to the bottom filling each space as it goes along.
The same is true in yoga practice. When I first began practicing some of the more difficult poses, I noticed I had a hard time with them, or they were still beyond my abilities. I couldn't quite get the faucet to reach that far. So I tipped my tray. I set them aside and just continued to pour time, energy, and effort into the basic poses. Sure enough, months down the road, and even if I hadn't tried the more advanced pose since, I would try one and see that I could assume the pose or do it with much more proficiency - all because of my dedication to the basics.
So in short, a basic practice done repeatedly will develop the capacities of your body to make gains on the more advanced poses that you may only practice occasionally - or even rarely. Breathe in the basics. Keep pouring your time and energy into the basics and let those flexibility, stability, and calmness gains cascade down to the other more formidable postures. You'll be surprised just how capable your body can be in time and with practice.
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