The Bible contrasts walking in the Spirit with walking in the flesh. To walk in the flesh is the natural state of all human beings. It means to allow your own ideas and opinions and perspectives to govern your words, decisions, and actions. To walk in the Spirit means to allow the Spirit of God to govern your words, decisions, and actions. To walk in the Spirit, a person must first be filled with the Holy Spirit, but then must yield to the Spirit.
Romans 8:5 says, 'For those who live according to the flesh set their minds on the things of the flesh, but those who live according to the Spirit, the things of the Spirit.' This verse tells us that if we are to walk in the Spirit, we must focus our minds on the things of the Spirit. This is virtually the same as saying that we must learn and think about the Word of God. The Word is what gives definition to the Spirit. We cannot walk in the Spirit if we do not know the Word. David wrote, 'My eyes are awake through the night watches, that I may meditate on Your word' (Psalms 119:148). This is what it means to set your mind on the things of the Spirit.
To walk in the Spirit is equal to walking in love (Ephesians 5:2); walking in truth (3 John 3-4), and walking in faith (2 Corinthians 5:7).