God's creation is a process--it had a beginning, and His followers have learned more and more as He works in history. The Christian life is also a process; we're not born fully grown and in armor like Athena from the head of Zeus. John, in I John 2:12-14, gives a quick overview of the process.
As we are physically born as a small, helpless baby, we start as spiritual children. Our first step is to recognize God as Father, and be willing to give up our sins and be forgiven. As we grow stronger, and have the Word living in our hearts and minds, we are ready to do battle with evil, and overcome through His strength. As we mature in the faith, we grow to know Christ more and more, and understand that He is from the beginning to time, a part of God Himself. We will never know Him completely on this earth, but we do know that we will know Him, as He knows us, beyond time and space.
This helps us keep a proper perspective on our spiritual life. We shouldn't be discouraged if we don't get the "whole ball of wax" at the beginning. If we are learning to know the Father, and allowing Him to deal with the sin that is part of our inheritance (both from innate self-centeredness and from the environment around us), that is a proper start. Jesus used the term "born again" speaking to Nicodemus, who was a professional religious person, but there was something more needed: becoming a new creature from the inside out. It's not uncommon for someone new to faith to get depressed because life isn't suddenly perfect. Or, to become content with a simple childlike faith. One of my sisters-in-law taught an adult Bible study class for some years, and once had an elderly lady come to her and say, "Eloise, I have the same faith that I had as a small child." Eloise told me that she had to bite her tongue to avoid answering "Oh, you poor thing!"
None of us is at the same place spiritually as anyone else. Hopefully we are each growing, as Jesus did, "in wisdom and strength,and in favor with God and man." At best, this means that we can all encourage each other, and learn from each other. We can learn from the wonder of a child (I recall my kids having amazing questions and insights), and we can learn from the experienced saints. We can use our strengths to help those who need it, and mourn with those who are mourning; rejoice with those who have been blessed. We can pick each other up as needed; and not be afraid to ask, and receive. From babies to oldsters, we are all members of His family.