Clear example of moaning (Totally hypothetical situation):
"I don't want to fight Jones. He is big and GSP would hurt me less."
Clear example of ducking (Confirmed fact with date and time to happen):
Te boss calls and:
"Whe have saved UFC 151. You are fighting Sonnen, a MW coming from a loss that had no time to prepare."
Answer: "No I refuse to fight him." - UFC 151 joins Titanic on the bottom of the ocean.
Clear example of stepping up (Fact lies in history of UFC):
"I will risk my win streak record to fight on short notice the tough, bigger, hungry, never finished, nothing to lose Bonnar in his last fight and save UFC 153."