Musar על כתובות 134:12

2) As to the second answer of the idler that he need not work a whole day for a livelihood, but that a few hours suffices, the tanna says that for the needs of his soul, this is not sufficient, for "the time is short and the work is long." For even if all of his work and toil all the days of his life were devoted to the needs of his soul — the acquisition of the Torah of the L-rd and the fulfillment of His mitzvoth — of what account is his toil in his scant days for the needs of the life of his immortal soul in eternity? And this is the intent of "And if I am for myself" — If I devote myself entirely to my [immortal] self, that is, to my soul, the [essential] selfhood of a man, "what am I?" Of what account is my work in [such] scant days for [such] a long road? As Mar Ukva said when he saw the account of his charities on high: "A long road and a light load." For, given the length of the road, his "sustenance" was of no account; and, furthermore, he had wasted "half of his money."