While he enjoyed the party, it did bring home how real the threat they were facing was. Relaxing isn't really in the cards. The second it's alright to do so he commits himself to training. He's not going to lose anyone if he can help it. His blind determination keeps him from noticing Natasha right away. Once he does, he makes an effort to wind down so he can stop just in time for her to call him out.

"Hey." He turns to her, wiping sweat from his brow a second later. "Something going on?" Like she can't just say hello or something.