Hi, misterX, welcome to PsychCentral (PC).

What we say has to come from our head and heart working together. I would make sure you know what you are feeling and that you check with your partner to make sure you understand what your partner means, before you try to reply.

As I think you have noticed ("I often manage to confuse or insult my partner, or come across as disrespectful, or as if I didn't care about the relationship or other issue at hand") it is not the words that are necessarily tripping you up but how you express them? I would train myself to start with something like, "I am glad you brought this subject up; I am very interested in exploring it with you." so your intent is there from the get-go?

Here's a link I liked: http://www.drnadig.com/feelings.htm