“He will not let me catch my breath.” That is, I am filled with a multitude of afflictions. “He has filled me with bitterness, for indeed he is superior in power. Who, then, shall resist his judgment?” Job does not want to say simply that God is superior to him in power but also that God is able to do whatever he wants.
34. It is often an exercise of virtue to the just, to be subject to ills from without by themselves; but that the conflict of a complete trial may discipline their powers, sometimes at one and the same time they are rent with torments without, and chastened with temptations within. Hence the holy man declares himself to be full of bitterness, in that whilst he is bearing scourges outwardly, there is a heavier weight, which from the adversary's tempting he carries in his interior; but withal the force of his sorrow is abated by considering the equity and the power of the Smiter.
[AD 407] John Chrysostom on Job 9:18-19