"The expert spiritual master knows well how to engage his disciple's energy in the transcendental loving service of the Lord, and thus he engages a devotee in a specific devotional service according to his special tendency."
(Caitanya-caritamrta, Adi 1.35, Purport)
"There need be no anxiety over attaining perfection because if one follows the instruction given by the spiritual master he is sure to attain perfection. A spiritual master is expert in giving special instructions to each of his disciples, and if the disciple executes the order of the spiritual master, that is the way of his perfection."
(Srimad-Bhagavatam 4.8.71, Purport)
"To surrender to Krishna all at once is not generally possible, but as we serve Krishna more and more, we gradually become more and more surrendered at His Lotus Feet. So you please continue to serve Krishna in these ways you have mentioned, and do not feel that your service is any less valuable than that of others. In the transcendental loving service of the Lord, it doesn't matter whether we are working, cooking, painting, writing, chanting, or whatever, they are all the same. There are no such distinctions of higher and lower on the transcendental platform. The important thing is that we are engaging our time and energy in the service of the Lord. After all, we are so tiny, what can we do? Krishna sees simply that this time is being spent in His service."
(Srila Prabhupada Letter, February 25, 1968)
"If you cannot do something which is hard for you, you do anything for Krishna under the direction of spiritual master, you'll get perfection. It is not that 'I have to do this. I have to do that.' No. Krishna's service is manyfold. If one is unable to take one kind of service, the spiritual master can give him another kind of service. But both the services are accepted by Krishna."
(Srila Prabhupada Lecture, Mayapur, March 12, 1976)