Try this simple exercise to feel the impact of posture in your energy and mood.
Sitting in your chair, let your body collapse into a slouching or slumping position. How does the inside of your body feel? Is there a sense of being stuck or stagnant? Do you feel a flow of energy?
Now over-effort by strongly lifting the chest skyward and force the shoulder blades down the back and towards one another. Maintain a strong low back curve as you suck the belly towards the spine. Now observe. How does this position make you feel? Do you feel free or tightly wound? Does there seem to be a free flow moving through your body? Do you feel open-hearted and filled with compassion and love?
The key to any alignment, including asanas or simply sitting in a chair, is not so much in following set instructions, but rather using instructions to help find the best flow of prana (energy).
So, this time, start soft. On an inhale, allow you heart center (chest area) to feel as if its floating skyward. As you exhale, keep the heart lifted and glide the shoulder blades gently down the back. Next inhale as you lengthen the spine and maintain awareness of the low back curve tipping the top of the sacrum forward. Maintain the spinal length as you exhale and softly draw the low belly back and up. How's the energy flow feel now? Do you feel comfortable? Confident? Is the breath any easier than in the previous 2 exercises?
This is what your asana practice ought to feel like. One of the beauties of Hatha Yoga is finding the flow of prana inside. This prana is literally your life force. So, it only makes sense to work with finding and allowing its flow to be enhanced at all times.
Enjoy the practice!
Today is the first day of the rest of your life!