If you employ your senses always in the service of Krsna, your senses are already controlled. Just like your tongue. Your tongue asks you, "Go to the restaurant and eat some nice thing." But if you are a Vaisnava, if you have this vow that "I shall not allow my tongue to eat anything except prasadam," it is already controlled.
From Srila Prabhupada's lecture on Bhagavad-gita 1.43 — London, July 30, 1973