Dive In to Fullness

If the Holy Spirit is already here and he has already come to the Christian than why do we still need to be filled with Him? If He has come what else need He do?

Answer: You have all the Holy Spirit when you receive Christ as your Savior. The Holy Spirit has all of you when you are filled by Him. Pentecost doesn't need to be repeated but its effects need to permeate our lives.
Other questions to answer: What happens when the Holy Spirit fills our lives/ what are the effects of Pentecost? What is the product of God's Spirit dynamically permeating and controlling my being? Is it emotionally impactful?
What are the common internal products of the filling of the Holy Spirit?