Acts 11:22-24 The news about them reached the ears of the church at Jerusalem, and they sent Barnabas off to Antioch. 23 Then when he arrived and witnessed the grace of God, he rejoiced and began to encourage them all with resolute heart to remain true to the Lord; 24 for he was a good man, and full of the Holy Spirit and of faith. And considerable numbers were brought to the Lord.
Just as in the illustration above, you and I as Christians - whether new to the faith or converted for years - continue to live life in this world - with the batteries of the Christian walk needing recharged. We need empowerment. The Spirit-filled life can be likened to the repeated need to be recharged and influenced by the Spirit following one's conversion to saving faith. To be a Spirit-filled Christian is to be a Spirit-led, Spirit-empowered one.
It is only apropos that in the very first place that we find the name "Christian" being used to describe Jesus followers that it should be attached to this idea of being "filled with the Holy Spirit." Just as the new birth or regenerative work of the Holy Spirit constitutes the epicenter of conversion; the filling or empowering ministry of the Holy Spirit occupies the center of the post-conversion Christian walk. The filling of the Spirit enables me to become in experience of my sanctification (i.e progressive Christian growth) whom God has legally declared me to be in justification in salvation. As we find Barnabas to be a grand example of this precious truth of the Spirit-filled life, may those who are Christians heed the admonition of the Apostle Paul in Ephesians 5:18 - to be filled with the Holy Spirit.