Is it necessary to practice yoga everyday? Let's make it specific. One should practice yoga everyday and every moment. Yoga learning is an attitude of life and the understanding way of life. Asana practice should be regular and everyday for a yoga practitioner. Sadhana is a must and Abhyasa is the mean to achieve the goal of life.
We won't forger to eat everyday for our physical energy. At the same time, we should not forget to practice asana everyday since asana give us body and mind energy. Whatever how long you practice asana, it is better to practice for short time everyday than once or twice a week for long time. It is better to practice regular than impromptu. Everyday, systematically, regularly, without fail and with all interest are the keys for yoga practice according to Sivananda's instruction.