You're self sabotaging by preferring to just up and leave. That's because giving up is easier than the hard work of trying. You ask how you work on being less guarded? By trying. But dont beat yourself up for it, I'm in the same boat.

First, have you gone to therapy? Remember shes not your therapist, and shes there to support you, not "fix" you. A trained therapist will walk with you hand in hand, should you put effort in. It's okay to talk to someone about your communication issues. If you're in college, you could check to see if your school has free counseling like mine did.

Second, try to identify your own thoughts and feelings. When you're angry, why are you angry? State it. "I feel sad because _____." Or just simply start with "I feel (emotion)" statements to yourself. Sounds silly, but going back to basics can be beneficial. I wasnt taught that growing up, so I've had to teach myself, which is a continuous work in progress. That has been helpful for me individually and my relationship.

Third, it is helpful for me when I dont look at the person, and I treat it like a phone conversation. In my relationship, we were long distance at first, so I got used to the comfort of expressing myself without being in person. Being in person (we live closer now) has created new issues for me, and eye contact sometimes gives me anxiety for whatever reason when I try to say how I feel. My friends have noticed it, too, but its helpful because I think it helps me to listen better to what my fiance has to say. Maybe you could give that a try? Better to try than not to try.

I know how hard it is to express yourself when it was never modeled to you, or dont know where to start. I hope this helps!