If you’re stuck in the Gospels, your focus is primarily on you and your performance.
If you’re stuck in the Gospels, you think of Christ external to you, i.e. only at the right-hand of the Father in a distant heaven.
Here is Peter’s example of being stuck in the Gospels:
“(5) And beside this, giving all diligence, add to your faith virtue; and to virtue knowledge; (6) And to knowledge temperance; and to temperance patience; and to patience godliness; (7) And to godliness brotherly kindness; and to brotherly kindness love. (8) For if these things are in you, and abound, they make you neither barren nor unfruitful in the knowledge of our Lord Jesus Christ. (9) But he who lacks these things is blind, and cannot see afar off, and has forgotten that he was cleansed from his old sins. (10) Therefore the rather, brothers, give diligence to make your calling and election sure: for if you do these things, you shall never fall: (11) For so an entrance shall be ministered to you abundantly into the everlasting kingdom of our Lord and Savior Jesus Christ. (12) Therefore I will not be negligent to put you always in remembrance of these things, though you know them, and be established in the present truth.” 2 Peter 1:5-12
You might ask, “How do I add these things?” This depends on you and your diligence, not God. Adding things, like the above, points to law, not Christ (the Embodiment of Grace).
How do you improve? By what you do ….
In contrast in a parallel passage, Paul writes that hope comes through tribulation and the love of God in our hearts, not our diligence to add to ourselves.
“(3) And not only so, but we glory in tribulations also: knowing that tribulation works patience; (4) And patience, experience; and experience, hope: (5) And hope does not shame or disappoint us; because the love of God is shed abroad in our hearts by the Holy Spirit Who is given to us.” Romans 5:3-5
Tribulation brings patience, not you adding it, as Peter declares.
The sources between Peter and Paul are different. Their messages are different. Peter knew Christ externally in the flesh, therefore he tells us that it is up to us to add these things.
Paul was given the message of the indwelling Godhead-the three Persons so desperately wanted to love us and be with us, that They came to live in us.
The way we grow either depends on us or it depends on God. Law or Grace.
If you are stuck in the Gospels, it’s up to us.
If we know Their love inside us, we know growth only happens because of our depending on Them.