To not show your true feelings as you deal with an unpleasant situation. To be a "tough guy".
"Check him out. His kid died, his wife just left him, and he's passing a kidney stone. He hasn't shed a single tear. He's John-Wayneing his way through this."
A hardo is a person who tries extremely hard at everything. Most times a hardo will try very hard at things that do not require excessive effort. For example, sports practices, gym class, etc.
Wow did you see Jack at practice today? What a hardo!