Dig inside yourself. Inside there is a spring of goodness ready to gush at any moment, if you keep digging.
Just yesterday (November 21, 2017) while at my son's basketball game, we were talking with another parent about the lack of organization with the coaching staff (high school got flooded, students and teachers have to commute 45 minutes to another school for classes and sports, kids and teachers' homes flooded, extenuating circumstances, etc.). In other words, there are lots of excuses and reasons to give the staff the benefit of the doubt for why they are not organized and why they cannot communicate better. So this parent just went off on them. They complained and moaned and griped. This parent, too, was flooded and despite that, they still think that flooding and the extenuating circumstances are no excuse for lack of organization and communication with the coaching staff. Now, the most surprising thing about all this, was how un-miffed my attitude was compared to this parent. Perhaps my former self would have moaned and complained just as much as this parent did, but not my current self.
This is what Marcus is saying here. He's saying, "remember that others have had this experience before and they have reacted badly and it got them nowhere." Complaining accomplishes nothing! Leave the complaining to the complainers. Instead of complaining, use your efforts to solve the problem; how you can turn this obstacle to your advantage. I love his last statement: action is important, context is indifferent (meaning it doesn't matter).
Don't give up! Keep digging within; the goodness is ready to burst at any moment, but you have to keep digging - you have to keep trying!
(see also Citadel p. 261)