For it is absolutely necessary for the grace of God to leave, once a tried struggler has acquired a good taste of it in the beginning, so that he may be tested and become a practiced soldier of Christ.
And without such temptations, no one has ever ascended to perfection. This stage that we mentioned where many fall into delusion is the stage where the grace of God withdraws in order to make us, as we have said, practiced soldiers of war, so that we are not infants forever. But the Lord wants us to become worthy men and brave fighters able to guard His riches. That is why He allows us to be tempted.
Elder Joseph the Hesychast