(Lord Sri Krishna—click to enlarge)
"In this endeavor there is no loss or diminution, and a little advancement on this path can protect one from the most dangerous type of fear."
"Activity in Kṛṣṇa consciousness, or acting for the benefit of Kṛṣṇa without expectation of sense gratification, is the highest transcendental quality of work. Even a small beginning of such activity finds no impediment, nor can that small beginning be lost at any stage. Any work begun on the material plane has to be completed, otherwise the whole attempt becomes a failure. But any work begun in Kṛṣṇa consciousness has a permanent effect, even though not finished. The performer of such work is therefore not at a loss even if his work in Kṛṣṇa consciousness is incomplete. One percent done in Kṛṣṇa consciousness bears permanent results, so that the next beginning is from the point of two percent; whereas, in material activity, without a hundred percent success, there is no profit."
(Bhagavad-gītā As It Is 2.40, Purport)
"Once engaged in the devotional service of the Lord, one will continue the service in all circumstances. In the Bhagavad-gītā it is said that even a small quantity of devotional service can save one from the most dangerous position. There are many instances of such examples in history. Ajāmila is one of them. Ajāmila in his early life was a devotee, but in his youth he fell down. Still he was saved by the Lord at the end."
(Śrīmad-Bhāgavatam 1.5.17, Purport)
"The time one devotes in a Kṛṣṇa consciousness temple cannot be taken away. It is an asset—a plus, not a minus. The duration of life, so far as the body is concerned, may be taken; however one tries to keep it intact, no one can do it. But the spiritual education we receive in Kṛṣṇa consciousness cannot be taken away by the sun. It becomes a solid asset."
(Easy Journey to Other Planets, Chapter 2)
"If we practice devotional service in this life, even for few days, still, it will be a permanent asset."
(Srila Prabhupada Lecture, Bombay, November 25, 1974)
"If sometimes one falls down, without... Then, yatra kva vā abhadram abhūd amuṣya kim. Then what is the loss there? He's not a loser. Still he's gainer. Because for the time being, whatever he has done sincerely, serving Kṛṣṇa, that is credited forever, eternally. It will be never lost. Mind that. Do sincerely, and you'll be never lost. Kaunteya pratijānīhi na me bhaktaḥ praṇaśyati (BG 9.31), Kṛṣṇa says, 'My dear Arjuna, you declare it, that none of My devotees will ever be vanquished. I'll give you protection.' Ahaṁ tvāṁ sarva-pāpebhyo mokṣayiṣyāmi (BG 18.66).
So do it sincerely. Don't think that 'Even if I fall, there is no loss.' No, don't think like that. Why I shall fall? I've taken to Kṛṣṇa's shelter, why shall you give it up? This is my life. But even if you fall down, that is also said, so there is no loss. There is no loss because, suppose if you have executed fifty percent, fifty percent you could not do; you fall down again... In another place it is also said, yoga-bhraṣṭo 'bhijāyate. Śucīnāṁ śrīmatāṁ gehe yoga-bhraṣṭo 'bhijāyate (BG 6.41). Yoga-bhraṣṭa: falling down from devotional service, he gets next chance again. He gets birth in very good family, rich family, and pure family, brāhmaṇa family, so that again he'll be given chance: 'Now, you begin again.'"
(Srila Prabhupada Lecture, London, September 13, 1973)
"Even by sentiment one comes to Kṛṣṇa consciousness and discharges the regulative duties, chants Hare Kṛṣṇa, his next life is guaranteed as a human being. Even he does it for some time—he is not perfect—still, his next life is guaranteed. But others, there is no such guarantee. Even if he discharges his so-called duties, material duties, there is no guarantee that he'll become a human being."
(Srila Prabhupada Morning Walk, Nairobi, November 2, 1975)
"Devotional service is so pure and perfect that once having begun, one is forcibly dragged to ultimate success."
(Nectar of Instruction 3, Purport)
"In a firm relationship with the Lord, the devotee does not give up the Lord's service under any circumstance. As far as the Lord Himself is concerned, if the devotee chooses to leave, the Lord brings him back again, dragging him by the hair."
(Caitanya-caritāmṛta Madhya 15.154, Purport)