why does ahab call himself a fool

Ahab call himself a fool because he left his wife, gave up all he had, and sacrificed forty years of his life chasing a whale...

"Aye, I widowed that poor girl when I married her, Starbuck; and then, the madness, the frenzy, the boiling blood and the smoking brow, with which, for a thousand lowerings old Ahab has furiously, foamingly chased his prey—more a demon than a man!—aye, aye! what a forty years’ fool—fool—old fool, has old Ahab been!"