When we use the word “self-control,” we do not mean that we become controllers exactly, but that we agree to be under Krishna’s control. The Bhagavad-gita describes the characteristics of the self-controlled: he withdraws his senses like a tortoise withdraws his limbs into its shell. Even though many rivers enter the ocean, the ocean remains unchanged. Similarly, a self-controlled person may experience many desires, but he remains unchanged by them. His basis of self-control is his trust that Krishna is supplying his necessities. Therefore, he can become fixed in his determination to surrender to Krishna.
(SB 4.11.11 Kaunas, September 1995)