Rom. 8:15 For you did not receive the spirit of slavery to fall back into fear, but you have received the Spirit of adoption as sons, by whom we cry, “Abba! Father!”
Jesus taught us that unless we are converted and become like little children we can never enter the kingdom of God. The world tends to harden us and take away those child like qualities that are so precious. That’s why Jesus said we must be converted and become like children. It is that new nature, that Christ like nature, that brings the innocence of childlikeness into our lives again. We become His children when we are born again. We are adopted as His children. This is much more than just a legal arrangement, He actually sends the Spirit of adoption, the Holy Spirit to live within us. We take on His nature. This brings incredible revelation to us, especially that we are dependent on God like a new born depends on His father, Abba Father is about all we can muster. Here are some comments from Matthew Henry on this verse.
“But you have received the Spirit of adoption. Men may give a charter of adoption; but it is God’s prerogative, when he adopts, to give a spirit of adoption—the nature of children. The Spirit of adoption works in the children of God a filial love to God as a Father, a delight in him, and a dependence upon him, as a Father. A sanctified soul bears the image of God, as the child bears the image of the father. Whereby we cry, Abba, Father. Praying is here called crying, which is not only an earnest, but a natural expression of desire; children that cannot speak vent their desires by crying. Now, the Spirit teaches us in prayer to come to God as a Father, with a holy humble confidence, emboldening the soul in that duty. Abba, Father. Abba is a Syriac word signifying father or my father; pater, a Greek work; and why both, Abba, Father? Because Christ said so in prayer (Mark xiv. 36), Abba, Father: and we have received the Spirit of the Son. It denotes an affectionate endearing importunity, and a believing stress laid upon the relation. Little children, begging of their parents, can say little but Father, Father, and that is rhetoric enough.”
So that yearning to cry out comes from God, no need to try to stop it, it’s okay for babies to cry. In that sense we will always be God’s babies, He loves to hear us cry Abba Father.