It's the ego that has the urge or desire to be in control of anything or everything.
Void of the ego, or the idea of 'I', there's none being there urging or desiring to control anything, but merely the law of cause and effect influencing all kinds of selfless impermanent names and forms being what they are, as they are.
Some minds think and believe that 'self-control' is about the ability to be controlling the body and mind to be and not to be in certain way, according to the desire of craving and aversion of the mind under the influence of passionate egoistic behavior pattern, rejecting selfless impermanent changes that are not necessarily the way that the mind desires it to be. "I am in control of myself, my body, my mind, my feelings, my life and my world. Everything is in my control to be the way that I desire it to be." Neither it's about to behave and not behaving or to live life and not living life in certain way according to certain worldly thinking, belief, values and practice about what is right and wrong, good and bad, or meaningful and meaningless.
In yoga or buddhism, the practice of self-control is referring to the will-power and determination to purify, discipline and quiet the mind, to prepare the mind for self-inquiry and meditation. It's more about letting go the egoistic urge or desire to be in control of anything, developing non-attachment and preparing the mind to stand as a witness or observer towards the selfless impermanent modification of the mind.
In the beginning of the practice, the impure egoistic mind has many impure thoughts, actions and reactions out of selfish intention or desire under the egoistic behavior pattern, that leads to restlessness, distraction and disturb in the mind, which hindering the mind from performing self-inquiry and meditation, and hence, there's a need to have certain degree of self-control or will-power to restrict or filter its own thoughts, actions and reactions, to purify, discipline and quiet the mind by weakening and removing egoism and impurities, for rendering the mind turning inwards and be open, not running out chasing after the objects of the senses, and being unattached towards any particular worldly egoistic thinking, belief, values and practice to analyze and judge everything, to be ready for self-inquiry and meditation.
It's not so much about do good and don't do bad, based on certain worldly egoistic thinking and belief, however, in the process of focusing onto purifying and disciplining the mind, filtering and restricting the thought activities, actions and reactions, naturally, there's no intention or desire, energy or effort, to be performing any actions that will be harming oneself and/or others.
Upon reaching a purified undisturbed egoless and desireless state of mind, there's no need to have self-control towards the modification of the mind that is free from impurities and disturbs, where the thought activities, understanding, actions and reactions are free from the influence of egoism and impurities, or selfish impure intention and expectation.