Process
Tony is used to this chain of events: action – reaction. It's perfectly logical and scientifically proven, and Tony adores logic and science. Maybe because they saved his live a good deal of times, maybe because he's just a tad scared of what's beyond.
As it turns out, it's Steve that's beyond.
It takes Tony months to realize that, though. He just isn't used to slow processes; everything in his life has been run before you walk; speed and adrenaline and constant stimuli, Iron Man being the best example. He's an epitome of twenty first century in this matter. And Steve just – gradually – happens.
First, it's not arguing and tentative apologies. Later, Steve moves in with everyone and starts to appear around the Tower, making breakfasts, looking for books, drawing one view or another, checking on everyone. Then everyone starts to narrow down to Tony; Steve lies to himself it's because the genius is bad at taking care of himself.
There is no action – reaction here, no questions and answers. One day, Tony just finds himself looking for Steve's hand to hold, out of blue, or so he believes.
Steve smiles. He's the man from different times. He can be patient.