God created every living creature to produce after its own kind and grow. There is a marvelous beauty inherent in new life it grows. As humans created in the image of God, we are to go through stages of growth.
"…like newborn babies, long for the pure milk of the word, so that by it you may grow in respect to salvation" (1 Pet 2:2),
In order to grow "in respect to salvation," we need to be in the word of God. It is interesting that the imagery used in this passage is of a nursing baby being nourished with his mother's milk. The word of God is what nourishes us and helps us to grow. Like a hungry baby, we need to long for it, drink it in, and do it often. We need to move from being spiritual "infants" to maturity and not get stuck:
"…you have need again for someone to teach you the elementary principles of the oracles of God, and you have come to need milk and not solid food. For everyone who partakes only of milk is not accustomed to the word of righteousness, for he is an infant. But solid food is for the mature, who because of practice have their senses trained to discern good and evil. Therefore leaving the elementary teaching about the Christ, let us press on to maturity" (Heb 5:12b-6:1a),
We begin with "elementary principles," then graduate to the next level. Pressing on to maturity is about learning and about putting it into "practice." It is about "training" to live life as a Christian in all aspects:
"…but speaking the truth in love, we are to grow up in all aspects into Him who is the head, even Christ" (Eph 4:15).
As we speak the truth in love, we are to "grow" in "all aspects" into Christ. As humans, there are several "aspects" of who and what we are. We are created as physical, emotional, intellectual, and social beings. We are also spiritual beings, which includes all of these. In passages such as Colossians 3, which describes the transformation that takes place in our lives when we are raised with Christ (Col 3:1), and have received the Spirit (Acts 2:38), who "renews" us (Tit 3:5), it becomes evident that being spiritual involves all "aspects" of our being, whether intellectual, emotional, social, etc. Our transformation involves the "renewing of our mind (Col 3:2; Rom 12:1-2). It involves a change in our emotional self, the way we react and deal with difficulties (Col 3:8). It involves a change in the nature of your relationship with brethren, your family, etc. (Col 3:18-4:1), and with those who are not brethren (Col 4:5).
So, even when our bodies stop "growing," we still continue to grow intellectually, emotionally, socially. We grow spiritually. You cannot be spiritually mature and yet be emotionally immature. You are a unit made up of all of these things, which are connected and affect each other. If you are not emotionally healthy, it can affect you physically and relationally. Everything is tied together and we need to tend to each one as part of our spiritual growth.