Evidently, Cain was pleased with his offering to the Lord because it was a result of his own labors, and he was probably a good farmer. Now the curse hit him where he felt it most—in his vocation. From henceforth, Cain would be a bedouin or a vagabond, taking of that which grew of itself or taking from another man’s labors. Nomads picked dates when they were ripe, etc., and just wandered, living from hand to mouth with no harvesting and storage.
Notice that Cain put being excluded from God’s “face” (that is, from His presence) second, not first, as it should have been. Instead Cain first mentioned being driven out from “the face of the earth.” No doubt Cain had a big farm, and having to leave his “earth,” his possessions, his home, was his first concern. He felt that loss very keenly. And then he realized a third thing: that his rejection would follow him into succeeding generations as men would begin to multiply. Cain felt this burden was too much. The statement “My punishment is greater than I can bear” brings in all three aspects of what Cain felt was his punishment: (1) being excluded from his home and property, (2) being excluded from God’s favor, and (3) fear of what others would do to him (that they would “slay” him).