In his book The Tree of Yoga, BKS Iyengar makes the following statement:
‘There are three transformations which take place in meditation. At the very beginning of his Yoga Sutras, Patanjali says that stillness of the mind is yoga. Later, he says that when a person is trying to still the mind, there is an opposition which occurs as new thoughts or new ideas arise in the mind. There is a tug-of-war between restraint and the rising thoughts as they come together.’
Iyengar BKS. Tree of Yoga, p145