As her leader and head, he must love her. All that he does must be consistent with her highest and best interests. He should never make an important decision without consulting her. He should always seek her best interests. It is difficult to think, on a glorious wedding day that a man would ever struggle with this evil thing called bitterness toward his dear bride, but if the Apostle warns of it, it is a danger.
Bitterness is angry resentment.
In the Bible it is associated with a feeling of being provoked or rebellious and with cursing and poisonous words. The Apostle implies by his warning that bitterness is a peculiar problem of husbands. Husband, as a married man greatly increased demands are made upon you. Your freedom and independence are greatly diminished. Anger and bitterness may result.