C. Sean Mcgee said this quote

Infants never learn to soothe themselves to sleep. They learn, abandoned in seclusion, that no matter the volume of their despondence, no matter the force of their tears, when they are alone and frightened, no-one will ever come to their rescue. Infants do not soothe themselves. They merely surrender. And it is caged in their cribs where the infants learn, in the face of their demons, to remain silent and submitting.