“Paul saw the Gospel as more than a onetime-only kērygma for unbelievers. Evangelicals have long acted as though the Gospel was the right “medicine” for unbelievers, but that believers need to move beyond the Gospel and go on to other things, a movement from the “milk” to the “meat.” But this seems untrue—thoroughly out of step with the biblical witness. We believe, rather, that it is imperative to think of moving on from the “milk” of the Gospel to the “meat” of the Gospel. For in fact the Gospel is more profound and multifaceted than our finite minds can ever grasp. We never move on from the Gospel; we move on in the Gospel.” (Kindle Edition, 1842)
“We do not move from the milk of the Gospel to the meat of something else, but from the milk of the Gospel to the meat of the Gospel.” (2143)
[Packer, J. I.. Grounded in the Gospel: Building Believers the Old-Fashioned Way (p. 109). Baker Publishing Group. Kindle Edition.]
Crowdedship 
Good point — the Gospel continues to save me.
“The Last Battle” by C.S. Lewis: “Come further up! Come further in!”
There is always more to learn; we are becoming like Jesus, who is God, and so He is well beyond our capability to encompass. I can’t get my head around the “whole thing”. This doesn’t mean I need to stop working out my salvation.