This is an important chapter about resilience.
"The good and bad are in ourselves, and not in external things" (v. 1, p. 177). Your choice, as to how to react to the world and to your body and surroundings, defines everything. You can either choose to exercise virtue or vice. If you choose to exercise virtue, it will be to your advantage.
Take the simple understanding "that knowledge is good, and error is bad, so that even in regard to what is false, something good arises: that knowledge that it is indeed false" (v. 3, p. 177).
The same can be applied to health, illness, death, lameness and all externals.
Seek for and draw advantage from illness, death and lameness. Dig deep and you will gain the advantage - you will improve as a human being.
"Cease to attach such value to what is purely material, and cease to make yourselves slaves of things ... and ... of the men who are able to procure them for you or take them away from you" (v. 8, p. 177). If you cease to deeply value such things, they will not hold you enslaved.
Just as you can derive advantage from a sparing partner, you can derive advantage from any event in life.
The man who insults you, becomes your training partner. He trains you in patience; he helps you abstain from anger and he helps you remain gentle (see v. 9, p. 178).
Your neighbor who is a bad man is "bad to himself" but not to you (v. 11, p. 178).
Your attitude toward everything in life should be: "bring me whatever you wish, and I'll turn it into something good. Bring illness, bring death, bring destitution, bring abuse or a trial for one's life, and ... all of that will become a source of benefit" (v. 12, p. 178).
Confronted with death, "make it something that can bring you honor" (v. 13, p. 178).
Confronted with illness, then remain steadfast and serene and don't even pray for death (v. 15, p. 178).
"Whatever you present to me I'll turn it into something blessed and a source of happiness, into something venerable and enviable" (v. 15, p. 178).
Be sure to check this post out: http://www.rockyrook.com/2017/09/commentary-on-meditations-b58.html and watch the video of Johnny Cash's song Sue.