A repost from my fellow Greenpath Boracay Yoga batchmate, Tracy Que
Sirsasana (Śīrṣāsana) or the Headstand or the King of all poses. My favorite pose at the end of the primary series because it feels like the easiest thing for me to do. With minimal or even no weight at all on the head, all it takes to support you in this pose is strength in the arms, shoulders and the bandhas (they are internal locks that hold pranic energy within certain areas in the body).
I feel strong when in this pose that I am able to hold for more than 25 breaths. When I am upside down, I feel like it re-aligns and strengthens my spine, and the best thing of all is, I do experience a clearer mind. 
Here are the other benefits of Sirsasana when practiced regularly (by B.K.S Iyengar):
- Builds stamina.
- Alleviates insomnia.
- Strengthens the arms, legs, lungs and spine.
- Improves the function of the pituitary and pineal glands.
- Increases the hemoglobin content in the blood.
- Reduces the occurrence of heart palpitations.
- Relieves the symptoms of colds, coughs and tonsillitis.
- It tones the abdominal organs and improves digestion.
- It enhances blood supply to the brain and calms it.
- Increases intellectual clarity, will power and respiration.
I know it is just one pose among so many. But it is through my practice of each and every one of them that I have become more mindful of my strengths and even more in-tuned with my weaknesses. Day by day, as I gain maturity in my practice (mentally, emotionally and even spiritually), I am a witness to the healing powers of the Ashtanga yoga. Through this, I am constantly transformed and humbled each day of my life.
- Tracy Que