Source: Nama-Japa in the Yoga of Transformation by Sri Ramkrishna Das
Mother (Sri Aurobindo Ashram) has differentiated between those who do Nama-Japa and those who go deep in meditation and concentrate but do not practice Nama-Japa. She has said:"In fact, you can immediately see the difference between those who have a mantra and those who don't. With those who have no mantra, even if they have a strong habit of meditation or concentration, something around them remains hazy and vague. Whereas the Japa imparts to those who practice it a kind of precision, a kind of solidity: an armature. They become galvanized, as it were."