Use the character’s behavior. He may or may not be conscious of his problem, but it will come through in the way he acts toward others. He’ll be wary of people who are nice to him. He’ll try to maintain excessive boundaries. He’ll likely show discomfort when conversations get too deep or when other characters act particularly close with him (e.g. he might shy away from friendly touch like hugs or pats on the back).
You can also mix up the introspection by showing his thoughts about others as well as himself. Maybe he’s judgmental of or confused by other characters who have close and trusting relationships. Or maybe a part of him wishes he had a friendship like that but he believes it’s not an option (because he’ll never be that naive, because people always fail, because he’s unworthy of it, etc.). You might already be doing this, in which case this paragraph is pretty irrelevant.
But the easiest way to show someone’s struggle rather than telling it is to use their behavior to reflect their beliefs.
Fantasy/dystopian/sci-fi author. Mythology nerd. Worldbuilding enthusiast. Singer. Fan of classic literat