Diaphragm breathing has worked wonders for me. At first you start with 20 minutes twice a day while lying down with knees bent and feet on the bed . Actually at the end of the 20 minutes, you can really feel the hands warming up. ( This was Edgelow's promise to me and in my case, and it works like magic)
After doing it for almost 2 years, it has become an involuntary habit for me. It has helped me with my circulation and I don't have the extremely ice cold hands anymore. It has also helped me a lot because I don't have anymore anxiety and tightening of my chest muscles.