And we are witnesses of these things, and the Holy Spirit is also, Whom God has bestowed on those who obey Him.(Acts 5:32 AMP)We can only know and prove the fullness of the Spirit as we step out into the larger purposes and plans of Christ for the world.
Perhaps the chief reason why the Holy Spirit has been so limited in His work in the hearts of Christians is the shameful neglect of the unsaved and unevangelized world by the great majority of the professed followers of Christ.
His power is a great trust, which we must use for the benefit of others and for the evangelization of the lost and sinful world. Not until the people of God awake to understand His real purpose for the salvation of men, will the Church ever know the fullness of her Pentecost.