Hi Jack,
I am personally only capable of being in a relationship when I can openly speak with my partner. Without that base the relationship just doesn't last long. Now, there is always this problemn: in order to be able to lead such a relationship, it requires both parties to be strong, open minded and willing to work things out. What do you do if you miss some of those qualities?
IMO it is the same as in yoga. How strong is the desire to maintain the relationship or even better evolve it? If the desire is there from both sides you should be able to start discussing the things that bother you with her. So what do you do if you don't feel ready to discuss things? The topic might easily slip out of your hands ending in a disaster. That is why, IMO, carson adviced you to meditate. It will give you a stable mind. Which in return enable you to stay calm and reflected and keep the discussion under control. It might take you a while to get to a point where you feel stable, but believe me, it is worth to strive for it.
Concerning the abdominal breathing exercises: coming from this type of exercises, I can say that, the exercises are very relaxing, if done properly and never have triggered any overload symptoms in me or the people, with whome I was practicing. But then again, you might be different and react strongly to it. If this is the case, cut down the amount of time you spend practicing. In any case, I really recommend you to meditate twice a day. It will help you in your whole life.
Wish you the best!
Yaming