All that happens is an event either within your natural ability to bear it, or not. So if it is an event within that ability, do not complain, but bear it as you were born to. If outside that ability, do not complain either: it will take you away before you have the chance for complaint. Remember, though, that you are by nature born to bear all that your own judgement can decide bearable, or tolerate in action, if you represent it to yourself as benefit or duty.
Chapter 2 of Book 10 is a little cryptic. But all Marcus is really saying is along the lines of: do what you must to care for and live after the duty of the mortal body. The physical nature of your body requires you to eat and drink to stay alive. Do this, within reason. And that is the key idea - you don't have to live for the body, but rather your body lives for you and you, as a rational being, should focus on performing every act rationally. Rational, as Marcus points out, implies being social. My father often used to tell me, "do you live to eat, or eat to live?" His implication was that I needed to not eat for pleasure, or overeat, but rather I should eat for sustenance. As a side-note, a year or so ago, I learned it was Socrates who coined the phrase my father would often recite to me.
Chapter 3 of Book 10 is a fancy and roundabout way of saying, "don't complain - ever!" Marcus believes that with the proper perspective, we can bear anything without complaint. Personally speaking, I think we all need to vent every once in a while, but after venting, we should not stray too far from reason and realize that our attitude needs to be adjusted and we need to do our best to endure nobly; to suffer well.
(see also Citadel p. 184)