Ps 54:4

“But this man being troubled and made sad was praying, his eye being disturbed as it were on account of anger. But the anger of a brother if it shall have been inveterate is then hatred. Anger doth trouble the eye, hatred doth quench it: anger is a straw, hatred is a beam. Sometimes thou hatest and chidest an angry man: in thee is hatred, in him whom thou chidest anger: with reason to thee is said, "Cast out first the beam from thine own eye, and so thou shall see to cast out the straw from thy brother's eye." For that ye may know how much difference there is between anger and hatred: day by day men are angry with their sons, show me them that hate their sons! This man being troubled was praying even when made sad, wrestling against all revilings of all revilers; not in order that he might conquer any one of them by giving back reviling, but that he might not hate any one of them. Hence he prayeth, hence asketh: "From the voice of the enemy and from the tribulation of the sinner." "My heart hath been troubled in me." This is the same as elsewhere hath been said, "Mine eye because of anger hath been troubled." And if eye hath been troubled, what followeth? "And fear of death hath fallen upon me." Our life is love: if life is love, death is hatred. When a man hath begun to fear lest he should hate him that he was loving, it is death he is fearing; and a sharper death, and a more inward death, whereby soul is killed, not body. Thou didst mind a man raging against thee; what was he to do, against whom thine own Lord had given thee security, saying, "Fear not them that kill the body"? He by raging killeth body, thou by keeping hatred hast killed soul; and he the body of another, thou thine own soul. "Fear," therefore, "of death hath fallen upon me."”

“"My heart was troubled." Here the magnitude of the tribulation is set forth with respect to three things: that it is close at hand, great, and efficacious. When someone wishes to exaggerate his pain, he says he has been struck to the heart. And therefore he says, "My heart was troubled within me"; as if to say: not in external things, but he is wounded to the very heart. Jer. 4: "My bowels are in pain." The tribulation is also great, because no evil among worldly things is as great as death. Hence he says, "The dread of death," that is, the fear of death, "fell upon me," because Saul wanted to kill him. The tribulation is also efficacious, because when fear is strong, it has a twofold effect: one in the body, namely trembling; the other in the soul, namely trepidation. And therefore he says, "Fear and trembling of death came upon me," that is, upon my powers with respect to the soul, "and darkness covered me," that is, stupor enveloped me. Or "darkness," that is, evil men. Ps. (117): "They surrounded me like bees."”