The Kingdom of heaven suffers violence:

The Lord says that "The Kingdom of heaven suffers violence, and the violent take it by force.' In the writings of the Apostle Paul we find that the matter of salvation does not depend upon us at all and that before our birth, God has determined for us one fate or another. What is the realtionship between the Divine provision and our free will? Answer: The fact that the Kingdom of God is 'taken by force' presupposes personal effort. When the Apostle Paul says, 'it is not of him that wills,' this means that ones efforts do not produce what is sought. It is necessary to combine them: to strive and to expect all things from grace. It is not one's own efforts that will lead to the goal, because without grace, efforts produce little; nor does grace without effort bring what is sought, because grace acts in us and for us through our efforts. (God's) foreknowledge is unfathomable. It is enough for us with our whole heart to believe that it never opposes God's grace and truth, and that it does not infringe man's freedom. Usually this resolves as follows: God foresees how a man will freely act and make dispositions accordingly; Divine determination depends on the life of a man, and not his life upon the dermination.

St. Theophan the Recluse, An Explanation of Certain Texts of Holy Scripture