Bhagavan's famous instruction 'summa iru' [be still] is often misunderstood. It does not mean that you should be physically still, it means that you should always abide in the Self. In sattva guna [a state of mental quietness and clarity] there is stillness and harmony. If mental activity is necessary while one is in sattva guna it takes place. But for the rest of the time there is stillness. If sattva guna predominates one experiences peace, bliss, clarity and an absence of wandering thoughts. That is the stillness that Bhagavan was prescribing