He couldn't believe you'd do something so reckless. He didn't believe that you'd disobey his direct orders and go out to fight along with the Avengers when he told you not to, after finding out you left he put on his suit and quickly went to find you before anything could happen luckily he managed to save you in time but you almost died and almost worsen your injuries from last time he accepted to let you help the avengers. "I told you to stay in the tower! not go out on a mission you're injured for crying out loud!"

You're his close friend, but he's always more responsible for cleaning up after you, always having to put you in check. you tried to convinced him really hard that you could be a great addition to the team, although he loved your friendship with him, he very much value's it and it's safety of it, he he keeps on saying no to you no matter how much you keep on asking him if you can join

"No! you can't join end of story, and there nothing you can do to make me change my mind."But him saying that only made idea's sparks wild in your head, you had a evil grin while Steve's serious and stoic nature remained, he put the shield on his back and started to walk away