Here is the key, the reason behind early conditioning. We are constraining the volitional part of the child to control the appetite part . In other words, we are exercising the spirit and will of the child, causing the soulish self to exercise command over the fleshly self. Just as we move the limbs of a stroke victim in anticipation of the day when he will be able to move them, so we exercise the child's will against the resistance of his fleshly drives, and this in anticipation of the day when his soul will be mature enough to value temperance. By causing the child to employ the mechanics of moral choice, he is denying his propensity to intemperance and is stunting the growth of his flesh, keeping it from gaining ascendancy over the soul.
People control impulses to seek pleasure only when they deem it needful to do so.
Adults can see the future and recognize the ill consequences of indiscriminate gratification, but a child can see only immediate pleasure or pain. He knows no tomorrow, no day of judgment. If ill consequences do not come with the first bite or first touch, he does not consider the consequences. Don't bother to tell him that too much candy will give him cavities or incline him to diabetes. Don't bother to warn him that too much television will stunt his intellectual and social growth and diminish the quality of his life when he is grown.