Walking in the spirit and being filled with the Spirit are to different things but they usually go hand in hand.....Being energized by God the Holy Spirit is the key and yet many are baffled in their understanding of this matter. God, God the Holy Spirit's energy will draw you closer to God as you meditate on God. As you consider and meditate on the Son of God and His way of life when He was here on earth as well of His eternal words about the love of God and how to share it with others around you your draw Gods attention closer to you. Well that energy enables you to walk in the spirit by that energy of the Holy Spirit.....You remember the parable of the Foolish Virgins(the Christians who just profess that they are Christians), well they ran out of Oil. The Oil that gives them the energy to live a lovingly godly lifestyle. Being fueled by the Presence or Energy of God is the Wise thing to do and be and would only apply to the Wise Virgins. Prayer is also a form of meditation if it comes from the heart. Supplications are right and all but they are just one form of meditation there are many others. Including reading scripture with an attention to the heart for the purpose is to teach you how to be a better person.