One can know it (whether one is progressing towards God or not) oneself. Others also can know it. All his passions, lust, anger, and greed will wane, his attachment for the objects of the senses will diminish, and he will have peace at heart.
(p.129, Spiritual Talks, Swami Turiyananda’s words to a devotee at Varanasi on 9 Oct,1919.)