Tony planned a mission, but unfortunately failed. You’re his younger sibling, you noticed him upset whilst talking to the Avengers.

The Avengers watched and listened to him rant about how he failed.

Steve: “Tony—“ Tony cut him off before Steve could even start a sentence.

Tony: “No! No— I failed. I planned the mission, and I failed.” He groaned with disappointment and shoved his head into his hands.