I don't know the science of it, but I imagine that even if some body parts grow faster or slower than others, when your a child most of your body grows and matures at a similar rate so that no part is left behind and stunted. So that no part keeps the rest of the body from functioning properly in its increasing maturity.
After all, if the whole body is healthy except for a foot that doesn't work, then it's the whole body that is lame.
We need to consider this as the body of Christ. If you are seeking to grow and mature spiritually, but I am stagnating or struggling, that matters.
There's only so far one person can go if the rest of the body isn't coming with it.
It doesn't matter how good you think your relationship with God is, you can never go that far alone.
After all, the Church is not made up of a bunch of individuals who just happen to believe in the same God.
Imagine a family trying to function where everyone just considers themselves all separate people who just happen to share the same last name and no other connection or relationship.
We are one Body. We have one Spirit in us.
"Make every effort to preserve the unity the Spirit has already created, with peace binding you together.
There is one body and one Spirit, just as you were all called to pursue one hope. There is one Lord Jesus, one living faith, one ceremonial washing through baptism, and one God—the Father over all who is above all, through all, and in all."
If we are all part of the one body, then we should care how all the other members are going. That means not only the others in our church group, the ones we get along with it easily agree with, but all Christians, everywhere. Even the ones we avoid, who disagree with us, who we think are wrong or misled or stagnating.
And care about them with genuine love, not an inflated ego to 'get them to catch up with me'.
Because they aren't just a diseased foot attached to a healthy body. They are an imperfect foot attached to a weak leg, attached to a stiff hip, attached to a wounded torso...
You get the picture. None of us is where we need to be. To get there, to reach more of the spiritual maturity, to experience more of the presence of God we need go there together.
And best thing is that it's not just up to us - we don't have to find a way to hold it all together - God provides that. We just have to practise Love towards each other. Stop getting caught up in the ins and outs of our differences as if that's the most important, and focus on the relationship.
"Instead, by truth spoken in love, we are to grow in every way into Him—the Anointed One, the head. He joins and holds together the whole body with its ligaments providing the support needed so each part works to its proper design to form a healthy, growing, and mature body that builds itself up in love.
When the Body begins to heal together, then each and every member will benefit from and experience this healing too.
If you want to grow deeper with God, then pray for the body as much as or more than you pray for yourself.