Galatians 5:22-25
22 But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness,
23 gentleness, self-control; against such things there is no law.
24 Now those who belong to Christ Jesus have crucified the flesh with its passions and desires.
25 If we live by the Spirit, let us also walk by the Spirit.
22 But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness,
23 gentleness, self-control; against such things there is no law.
This list is the fruit, not of the self-effort of the Christian, but of the Holy Spirit. I point this out because Christians have the strange habit of reading this verse (and many others) and filtering it through their preferences, prejudices, and preconceptions 'til it transforms into a command to them to produce from their own human resources the "fruit" of the Holy Spirit. But only from the in-filling of the Spirit of Truth, love, holiness and grace do these characteristics arise. He is our love, he is our peace, he is our patience, and so on. How often though, believers set out to produce their best version of these things, thinking God is pleased by their fleshly counterfeit of the fruit of the Spirit that leaves them exhausted, knowing only the extent of their own limits more thoroughly, and with corrupted "fruit" (Ga. 6:7-8).
24 Now those who belong to Christ Jesus have crucified the flesh with its passions and desires.
Perhaps Paul anticipated that some of his readers would attempt to form from their own fleshly powers (intellect, will, and physical strength) the "fruit of the Spirit" and so, he points out that those who belong to Christ have "crucified the flesh" - a necessary precursor to "walking in the Spirit." Why? Because "in my flesh dwells no good thing" (Ro. 7:18), because "the mind set on the flesh is at enmity with God" (Ro. 8:7-8), because the flesh is at war with the Spirit (Ga. 5:17). Any Christian, then, who is striving to produce the fruit of the Spirit from their own flesh-centered-and-empowered effort is doomed to failure. From such effort, they may form a rough facsimile of the supernatural life and work of the Spirit, but because that facsimile is fundamentally a thing of the flesh (intellect, will, physical strength), it is corrupt, weak and very displeasing to God. And so, Paul urges his readers in the verse above to remember that they've been crucified with Christ that "the body of sin might be destroyed that henceforth they should not serve sin" (Ro. 6:6).
25 If we live by the Spirit, let us also walk by the Spirit.
The emphasis in this verse is entirely upon the Spirit, not the actions of the believer. The born-again person lives in/by the Spirit. They have no life spiritually apart from what they receive from the Spirit; they cannot work up his life from their own fleshly effort; they cannot please God in the attempt to do so. Only by the indwelling Spirit working into them his life, filling them with himself, can they then "work out their salvation with fear and trembling." (Phil. 2:12-13).
But the majority of believers, in my experience, think they're in a more-or-less equal partnership with the Spirit, that he's their "co-pilot," a divine Assistant, who shores up them up when they've exhausted their own reserves of fleshly power in "living the Christian life." In reality, just as they could only receive life from the Spirit, they can only receive from him the power to act out, or work out, their salvation in their daily living. And so, Paul wrote, "let us also walk BY (or in) the Spirit," not "let us walk by our own fleshly effort."
How many are the Christians, though, who live for years trying to be godly by self-effort, setting themselves to the laborious (and impossible) task of producing from their own human powers a God-pleasing life. "I'm a Christian, so I'd better act like it," is their reasoning. And so, in accord with the old Nike "Just Do It" tag-line, they begin to pull themselves up spiritually by their own boot straps. They can seem to succeed - briefly - too, but that "success" is entirely a work of their fleshly powers, God not at all involved. Since the result of this fleshly effort has a pious, "Christian" veneer, it is accepted by the Church, utterly apart from God though the effort has been.
This isn't "walking in the Spirit." Not even close. It's just a fleshly counterfeit of what walking in the Spirit is. Actual walking in the Spirit happens only under a specific, God-commanded circumstance: The Spirit only enables the child of God with his supernatural life and power to live "godly in Christ Jesus" when the child of God is persistently and consistently submitted to the will and way of God, yielding to Him repeatedly throughout each day (Ja. 4:7-10; Ro. 6:13-22; Ro. 12:1; 1 Pe. 5:6, etc.).
But every time a believer indulges an evil thought or attitude, or imagines some ungodly motive or conduct in another believer, or surrenders to an inordinate impulse of the flesh (i.e. any addiction), or runs ahead of God's leading, forging their own course, or satisfies some selfish desire in a sinful manner, they depart the Spirit's control. Until they consciously, explicitly submit to him once again (Lu. 22:42), they cannot "walk in the Spirit." They are rebels, actually, until such time as they repent of their waywardness and sin, confess it and yield once more to God's will and way (Ja. 4:8-10; 1 Jn. 1:9; Ro. 6:13). The Spirit does not empower and transform rebels against their will.
And so, there are many born-again believers who have been given spiritual life by the Spirit who are not walking in his power, transformed by him, his "fruit" truly evident in their lives. They're working very hard, though, to form their own corrupt, human version of his supernatural life and power, imagining - wrongly - that God is pleased with their effort. And so, these straining, striving believers are just as those ignorant Jews whom Paul described:
Romans 10:2-3
2 For I bear them record that they have a zeal of God, but not according to knowledge.
3 For they being ignorant of God's righteousness, and going about to establish their own righteousness, have not submitted themselves unto the righteousness of God.