Quote from : Captain America: The Winter Soldier Movie

Steve Rogers: You just can't stop yourself from lying, can you?
Nick Fury: I didn't lie. Agent Romanoff had a different mission than yours.
Steve Rogers: Which you didn't feel obliged to share.
Nick Fury: I'm not obliged to do anything.
Steve Rogers: Those hostages could have died, Nick.
Nick Fury: I sent the greatest soldier in history to make sure that didn't happen.
Steve Rogers: Soldiers trust each other. That's what make it an army. Not a bunch of guys running around shooting guns.
Nick Fury: Last time I trusted someone, I lost an eye. Look, I didn't want you doing anything you weren't comfortable with. Agent Romanoff is comfortable with everything.
Steve Rogers: I can't lead a mission when the people I'm leading have missions of their own.
Nick Fury: It's called compartmentalization. Nobody spills the secrets, because nobody knows them all.
Steve Rogers: Except you.
Nick Fury: You're wrong about me. I do share. I'm nice like that.