Acts 4:29-31 "And now, Lord, look upon their threats and grant to your servants to continue to speak your word with all boldness, while you stretch out your hand to heal, and signs and wonders are performed through the name of your holy servant Jesus." And when they had prayed, the place in which they were gathered together was shaken, and they were all filled with the Holy Spirit and continued to speak the word of God with boldness.
Many Christians want to be filled with the Spirit just so that they can get an "experience." But the anointing of the Spirit is not given to make us feel good but to empower us to fulfill God's Kingdom vision in Christ. In other words, it is the same reason the Spirit came on Jesus at river Jordan, to empower Him to preach the Gospel to the poor, to proclaim freedom to captives, to open blind eyes and to proclaim the year of the Lord's favour (Lk 4:18). It's not just to meet our own emotional and spiritual needs, but to fulfill God's vision and purpose.
It's only as we are aligned with God's Kingdom purpose, to join Jesus in His continuing ministry among us to save and heal that we will be filled with the Spirit spontaneously as it happened to the disciples. If we are self-seeking and self-centred, focusing on building our own business empire and career, we are unlikely to remain filled with the Spirit. But if we build our business and career in order to advance God's Kingdom then we will be filled continually with the Spirit.
Our prayers reflect our personal priority: if it is self-focused, then we will not expect the Holy Spirit's anointing to increase. But if our prayers are like the disciples, focused on preaching Christ, then we have a strong ally in the Holy Spirit. We will be continually filled as we continually proclaimed the Gospel.