I used to have to run to the bathroom at dinner because I'd have the strong urge to throw up. For reasons I don't understand, that problem went away gradually in my late teens.
But I still retain a habit from those days that helps me get through the times when I cough so hard I feel like my stomach's going to chuck up everything: I pinch the pressure point on my left hand - the meat between the thumb and pointer finger - with my right thumb and pointer finger, and then I pick one thing to look at and stare at it, focusing on it completely. It's weird, but it works. It calms the breathing, and helps the nausea go away.
But I still retain a habit from those days that helps me get through the times when I cough so hard I feel like my stomach's going to chuck up everything: I pinch the pressure point on my left hand - the meat between the thumb and pointer finger - with my right thumb and pointer finger, and then I pick one thing to look at and stare at it, focusing on it completely. It's weird, but it works. It calms the breathing, and helps the nausea go away.