Here "hold fast" is a metaphor that represents being determined to continue to say something. The abstract noun "righteousness" can be expressed with "righteous." AT: "I am determined to continue saying that I am righteous" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-abstractnouns]])
Here "will not let it go" is a metaphor that represents not stopping saying something. AT: "will not stop saying that I am righteous" or "will not stop saying so" (See: [[rc://en/ta/man/translate/figs-metaphor]])
# my thoughts will not reproach me
Here the phrase "my thoughts" represents Job. AT: "even in my thoughts, I will not reproach myself" (See: [[rc://en/ta/man/translate/figs-metonymy]])