We can only know and prove the fulness 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. There are millions of professing Christians -- and, perhaps, real Christians -- in the world, who have never given one real, earnest thought to the evangelization of the heathen world.
God will not give the Holy Spirit in His fulness for the selfish enjoyment of any Christian. 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 fulness of her Pentecost. God's promised power must lie along the line of duty, and as we obey the command, we shall receive His promise in his fulness.
Lord, help me to understand Thy plan.