To hold composure, even in the stickiest of situations; to be a juggernaut with grace 100 percent of the time...every time. It may be used at times when someone may be feeling doubt, fear, anger, sadness, nervousness, agitated, shame, or like a pussy; generally among friends. It is the only appropriate remedy when the speaker finds their friend or acquaintance at their lowest state of being.
I opened the door one day to find my best friend soaking wet and crying, and he tells me that he has just lost his job, his wife has left him, his dog ran away, his car was stolen, and he's broke. I had never seen a man look so shockingly, depressed before. After a long pause, the only helpful words that I could think of were "Just maintain." The next day, my friend went big on the stock market and bought a new car, found his dog, got a job with a bigger firm, and had a Victoria Secret model offer to run away with him.