A rich and wise answer from Abraham Kuyper:
Dwelling in the elect, the Spirit does not slumber, nor does He keep an eternal Sabbath, in idleness shutting Himself up in their hearts; but as divine Worker He seeks from within to fill their individual persons, pouring the stream of His divine brightness through every space.
But we should not imagine that every believer is instantly filled and permeated. On the contrary, the Holy Spirit finds him filled with all manner of evil and treachery. . . . His method of procedure is not with divine power to force a man as though he were a stock or block, but by the power of love and compassion so to influence and energize the impulses of the feeble will that it feels the effect, is inclined, and finally consents to be the temple of the Holy Spirit. . . .
This operation is different in each person. In one it proceeds with marvelous rapidity; in another, progress is exceedingly slow, being checked by serious reaction which in some rare cases is overcome only with the last breath. There are scarcely two men in whom this gracious operation is completely the same.
It may not be denied that the Holy Spirit often meets serious opposition on the part of the saint. . . . And the Holy Spirit bears all this resistance with infinite pity, and overcomes it and casts it out with eternal mercy.
Who that is not a stranger to his own heart does not remember how many years it took before he would yield a certain point of resistance; how he always avoided facing it; restlessly opposed it, at last thought to end the matter by arranging for a sort of modus vivendi between himself and the Holy Spirit? But the Holy Spirit did not cease, gave him no rest; again and again that familiar knock was heard, the calling in his heart of that familiar voice. And after years of resistance he could not but yield in the end.
–Abraham Kuyper, The Work of the Holy Spirit (trans. Henri De Vries; Grand Rapids: Eerdmans, 1979), 529–30
(HT: Dane Ortlund)