My heart is smitten, and withered like grass
Like grass in the summer solstice F4, which being smitten with the heat of the sun, or by some blast of thunder and lightning, is dried up, and withers away; so his heart was smitten with a sense of sin, and of God's wrath and displeasure at him, and with the heat of affliction and trouble, that it failed him, and he could not look up with joy and comfort:
so that I forget to eat my bread;
sometimes, through grief and trouble, persons refuse to eat bread, as Jonathan and Ahab, which is a voluntary act, and purposely done; but here, in the psalmist, there was such a loss of appetite, through sorrow, that he forgot his stated meals, having no manner of inclination to food: some understand this of spiritual food, the bread of life, refusing to be comforted with it; so the Targum,
``for I forgot the law of my doctrine.''