Paul taught that when we walk in step with the Spirit we do the things that please God.

The indwelling Spirit is always in harmony with the will of God, is always motivated to do the will of God, and is permanently available to us to enable us to live out of this motivation and harmony.

For this reason also, since the day we heard of it, we have not ceased to pray for you and to ask that you may be filled with the knowledge of His will in all spiritual wisdom and understanding, 10  so that you will walk in a manner worthy of the Lord, to please Him in all respects, bearing fruit in every good work and increasing in the knowledge of God; 11  strengthened with all power, according to His glorious might, for the attaining of all steadfastness and patience; joyously 12  giving thanks to the Father, who has qualified us to share in the inheritance of the saints in Light. Colossians 1:9-12 (NASB) 

Walking in the Spirit describes the experience of the Holy Spirit demonstrating his supernatural ability to enable us to live above the downward pull of sin and the “flesh” and experience God’s guidance and empowerment to be effective representatives of the kingdom of God.

Because most people are only familiar with living out of their own strength and resources, the idea of living above the downward pull of sin seems unbelievable.

When we live out of our own strength, we are doomed to failure because we were never intended or designed to do that.

From the beginning God planned for all people to draw on his life and ability, but Adam and Eve chose the tree of the knowledge of good and evil over the tree of life. The tree of life represents living out of God’s resources in the Spirit. The tree of the knowledge of good and evil represents living out of our own resources, knowledge, and ability. That has not worked out very well. Sin is basically the disastrous attempt to be our own boss, our own source, and our own god.

The first step in learning how to walk in the Spirit is to admit we cannot do life on our own and surrender to the Lord Jesus.

Once we take this step, he gives us his Spirit to be our Helper, the One who is called alongside and who dwells within us. At that point we begin the lifelong process of learning to “lean not on our own understanding” (Proverbs 3:5-6), but to lean on the Spirit of God.

The Law of Lift

The laws of density and buoyancy describe how objects rise if they are less dense (more buoyant) than the medium around them. When objects encounter a less dense medium they stop rising. Likewise objects fall toward the ground until they encounter something more dense. For example, a ship made of steel can float on less dense water because there is so much less dense air in its hull. If the hull is breached and fills with water, it will sink until it encounters the more dense sea floor.

Airplanes are no exception. Since they are denser than air, how is it that they can fly? The answer is that, if a plane attains enough speed, the design of the wings causes the upward lift of slower moving air under the wings to push the plane upward. If properly designed and flown, a plane overcomes gravity, as long as the necessary airspeed is maintained. The law of lift temporarily overcomes the tendency of the dense structure of the plane to fall toward the more dense ground. If airspeed drops too far, so will the plane. The law of density and buoyancy has not been suspended, but temporarily overcome by the law of lift. This is a decent analogy of what it means to walk in the Spirit.

The Downward Pull of the “Flesh”

The downward pull of the flesh does not go away when we walk in the Spirit. It is overcome by the lifting power of the Holy Spirit.

We know that our old man was crucified with him so that the body of sin would no longer dominate us [Greek: katergeo], so that we would no longer be enslaved to sin. Romans 6:6 (NET1) 

I chose the New English Translation in the verse above because it properly translates the difficult Greek word, katargeo, which means either to render inoperative or to abolish. It is clear that the “flesh” or “body of sin” still can influence us after we are born again, but we no longer must obey it. We can now walk in the freedom of the Holy Spirit if we so desire.

But I say, walk by the Spirit, and you will not carry out the desire of the flesh. 17  For the flesh sets its desire against the Spirit, and the Spirit against the flesh; for these are in opposition to one another, so that you may not do the things that you please. Galatians 5:16-17 (NASB) 

Just as surely as a plane that loses speed will descend to encounter the ground; so, the “flesh” will pull us down into sin and carnality, if we do not continually overcome it by choosing to walk in the power of God’s Spirit.

God did not annihilate our “flesh.” Instead, he removed its power to dominate us, leaving us with the option to lean on him and experience victory.

This requires us to keep our focus on the Lord. It is helpful to devote ourselves to worship, prayer, Bible meditation, and whatever helps us to continually draw upon the resources of the Lord rather than our own.

The Fear of the Lord

A good pilot spends time inspecting his plane before takeoff because once in the air everything must be working properly or bad things can happen. God expects us to vigilantly look after the things that he has put under our responsibility, so that we can walk in the Spirit each day.

Therefore be careful how you walk, not as unwise men but as wise, 16  making the most of your time, because the days are evil. 17  So then do not be foolish, but understand what the will of the Lord is. 18  And do not get drunk with wine, for that is dissipation, but be filled with the Spirit, 19  speaking to one another in psalms and hymns and spiritual songs, singing and making melody with your heart to the Lord; 20  always giving thanks for all things in the name of our Lord Jesus Christ to God, even the Father; 21  and be subject to one another in the fear of Christ.  Ephesians 5:15-21 (NASB)  

A good pilot knows that attention to details can mean the difference between success and failure, life and death. You might say a good pilot has a certain good sort of fear in her or his approach to flying.

We likewise should maintain a proper fear of the Lord as we walk in the Spirit each day, realizing that we have a responsibility to make sure things are in order in our lives.

We have wicked spiritual enemies all around us who desire to sabotage our walk with the Lord, our own “flesh” being the most vile and untrustworthy.

So the church throughout all Judea and Galilee and Samaria had peace and was being built up. And walking in the fear of the Lord and in the comfort of the Holy Spirit, it multiplied. Acts 9:31 (ESV) 

Conclusion

To conclude, I believe that it is legitimate to compare walking in step with the Spirit to flying. When everything is working properly, there is no struggle in flying. The combination of a properly working plane and a good pilot creates a stress free experience of flight. Pilots, however, must be vigilant to inspect their planes regularly and do any needed repairs or maintenance. Likewise, spiritually speaking, even though we have been given all we need for success (2 Peter 1:3), we must never presume that walking in the Spirit allows us to become slack in our devotion to the Lord. Carefulness and vigilance, coupled with complete trust in the Lord, will allow us to experience the victory of the Spirit of life within us.

For the law of the Spirit of life in Christ Jesus has made me free from the law of sin and death. 3 For what the law could not do in that it was weak through the flesh, God did by sending His own Son in the likeness of sinful flesh, on account of sin: He condemned sin in the flesh, 4 that the righteous requirement of the law might be fulfilled in us who do not walk according to the flesh but according to the Spirit. Romans 8:2–4 (NKJV)