(Click to enlarge painting of Krishna)
Devotee: Śrīla Prabhupāda, how is one able to draw the distinction between working very hard for Kṛṣṇa and over-endeavoring?
Prabhupāda: Hmm. What is that—phalena paricīyate. By the result you can understand. By service Kṛṣṇa, he will understand more about Kṛṣṇa. Kṛṣṇa will be clear to him. That is the test. Because it is said, sevonmukhe hi jihvādau svayam. Kṛṣṇa cannot be realized by so-called speculation, but if you render service to Kṛṣṇa, then Kṛṣṇa will reveal to you. Revelation. So he, how much service he is giving, that will be tested how much he has, I mean to say, realized Kṛṣṇa. This is the test. If Kṛṣṇa is still vague idea to him, then he has not advanced. This is the test. Just like if you have eaten something, then you will feel satisfaction. You are hungry, you have been given some food, but you cannot say that "I am eating, also I am not satisfied in my hunger." That cannot be. If you are actually serving Kṛṣṇa, then Kṛṣṇa will reveal to you. You will know what is Kṛṣṇa, asaṁśayaṁ samagraṁ mām, without any doubt, and fullness. Here is the test. If somebody comes, "What is Kṛṣṇa?" You say, "Yes, I am serving Kṛṣṇa, but I do not know what is Kṛṣṇa," what is his service? He must know, because here it is said, asaṁśayaṁ samagram, without any doubt.
(Srila Prabhupada Lecture, Melbourne, June 29, 1974)