In short, Job believed it was useless for him to try to prove himself upright since God seemed determined to punish him. [source][source][source]
The Book of Job uses legal terms and metaphors extensively in the sections that deal with Job"s disputes with God. Job had previously served as a judge in his town ( Job 29:7-17), and he wanted justice (Heb. mispat) from God. [1] Therefore he used legal terminology frequently in his dialogues. These legal metaphors are one of the key features of the book since they help us identify its purpose. [2][source]
Job"s frustration, expressed in Job 9:32-33, is understandable since God was both his legal adversary and his judge. This accounts for his urgent yet hopeless cry for a neutral party (mediator, umpire) to arbitrate a settlement between himself and God. In the ancient Near East this arbitrator was a judge whose verdict was more often a settlement proposal that the litigants could either accept or reject (cf. Job 13:7-12; Job 16:18-21. [3] Job had no hope of receiving justice from God-only mercy ( Job 9:34). He felt that since God was so great, he could not vindicate himself. [source][source][source]
"This is the persistent problem, the real problem of the book: not the problem of suffering, to be solved intellectually by supplying a satisfactory answer which explains why it happened; but the attainment of a right relationship with God which makes existence in suffering holy and acceptable." [4][source]
""I am not like that in myself" ( Job 9:35) means "that is not the way it is with regard to my case."" [5][source]