I'm of the same mindset, and it's probably an unconscious defensive posture developed early on when I bought into the notion that everyone I encountered was a potential danger. That attitude stuck. Nowadays I often display a friendly or least okay disposition when I first meet someone; then something goes awry (and it can be very minor) that seems to set off a trigger that says “be careful” and it spirals down from there. I'm aware of it better, but it's pretty hard to resist the old habits.
Even the phrase “work on it” is always hard for me, probably because when young the premise of working at something frequently backfired, and my safety was to distrust the notion that mere working at something would accomplish anything. Now, if I remember to switch out “working on it” for “playing with options”, that seems to make it easier.
My prob is that even when it seems to go okay with other people, I run into one with red flags—just one—and my old self-protective instincts kick in as if to say DANGER AHEAD, get away. I've developed an inner “helper” that whispers things like “you're okay; safe; wonderful as you are”. This probably sounds hokey to some, but it helps me out, so I stick with it. The push-pull, stumbles, starts and false leads of the inner/outer critic is another hazard that threatens to wear one's resolve to a frazzle.
What I'd like to do is get to a point where the words are only pointers—we learn and forget 'em all anyway. But if we keep absorbing what we do learn, there's hope, and then we incorporate that too; to where it's not just possible to change, we gladly surrender to it. Sounds like your therapist has set a good starting point for you and I wish you well.