It's one of my favourite topics of screenwriting.
There really isn't a lot of room left.
Iron Man 2 is about him recognizing the need to not bear responsible for everything alone and let others into his life.
Tony vs. his PTSD/need to bear the burden
"How much for the gun?"
"Not for sale."
"How much for the arm?"
Bucky walks away.
"Oh, I'll get that arm."