Who decides how much of the Holy Spirit's fullness a believer keeps?
Within the realm of control God grants, the believer decides how much of the Holy Spirit's fullness to maintain. At salvation, God fills the believer to the brim with the Holy Spirit, but the individual then determines whether to keep that fullness or let it empty out through worldly attractions, temptations, and fleshly desires.
Les explains that the moment a person is saved, they have all of God as He can put Himself into them—the fullness of the Holy Spirit from the very moment they believe. You don't have to work for it or look for it; it was all part of salvation. However, God leaves within the believer's realm of control how much of that fullness they will maintain or whether they will let it empty out. Les uses a cup analogy: to fill a cup with air, you must pour out the liquid; if you pour out half, half is air; if you pour out three-fourths, three-fourths is air. The Holy Spirit is likened to air, or pneuma. A newly saved person is filled to the brim and bubbling over, but the world's allurements, temptations, and fleshly desires can refill the cup with material things until it is full of the material instead.