His Divine Grace A.C. Bhaktivedanta Swami Prabhupada:
"I remember one of our teachers in our school life, he
instructed that "If you always think that 'I shall pass my examination
with distinction,' then you can pass in first division. If you think that 'I
shall pass my examination in the first division,' then you may pass in the
third division. And if you think that 'I shall some way pass my examination in
the third division,' then you will fail." That means if you expect more
than your capacity, then it may be possible that at the time of examination you
get the right number and pass your exam.
So the chanting of Hare Krsna mantra, Caitanya Mahaprabhu
has said, sada, kirtaniyah sada harih: not that two hours or one hour, but one
should practice. And that is the recommendation as it was followed by Haridasa
Thakura. But because we cannot do that, therefore we have to engage always in
the service of Krsna. That will make me remembering Krsna. Real fact is how to
remember Krsna."
Srimad-Bhagavatam 6.2.12–14 -- January 17, 1971, Allahabad