The writer speaks of a person remembering what he has learned as if "instruction" were an object that the person can hold tightly. AT: "Continue to obey what I have taught you and never forget it" (See: [[rc://en/ta/man/translate/figs-metaphor]])
The writer speaks of discipline preserving a person's life as if it were that person's life. AT: "for it will preserve your life" (See: [[rc://en/ta/man/translate/figs-metonymy]])