Believe it or not. There is a right way and a WRONG way of breathing. Some of you may know and some of you may don't. Regardless, here is a link on what it's all about:
wwwDOTyoutubeDOTcom/watch?v=1WMt_1jw47Q (instead of "DOT" put and actual dot " . ")
That was a 3D video that show'd you what happens inside and how breathing should be. And here is another video on how to do it:
wwwDOTyoutubeDOTcom/watch?v=9yjtw5Jbmlw
Now, this may not be the most professional good looking video BUT listen to what he say's and what he does. I personally have been doing just that and here is my experience.
I was a chest breather was because a few months ago a thought passed in my mind "What if there is a right way of breathing?" I searched it on YouTube and to my surprise there WAS! Not only that there where hundreds of videos but breathing with your diaphragm was a practice that people would do for thousands of years.
So I watched some videos read a bit on google (some blogs, forums and experts websites) and decided on trying it because of the long list of benefits the one that I was most interested was that it could relieve me from my anxiety. So I decided to do it, plus that all I had to do is breathe in a certain way.
I can't remember exactly when I started because it was something that I used to do before falling asleep (I discovered that it helped me fall asleep faster) on occasions when I remembered and most of all when I felt anxious. One thing is for sure it's somewhere around half to a full year.
Today I was doing my daily routine and I remembered about this practice by seeing the Body section on this forum. Breathing with my diaphragm become'd such a part of me that now it is my normal way of breathing. I concentrate on it only when I'm meditating but when I wake up in the morning I wake up "belly breathing" which it's a clear sign that this is how I breath when I'm asleep of course since I started this practice my nightmares diminished incredibly and I rest better.
I tried to breathe again with my chest just of curiosity to see the difference and I found it to be uncomfortable, it feel weird and I can't seem to breathe "right" just only with the chest, my new pattern of breathing quickly kicks in. Also breathing with the chest now feels only 30% of my capacity of breathing.
Another difference that I felt and "heard" is my new awesome voice

. I speak more clearly, a better tonality, more relaxed and the feature which I love the most is much deeper. Also I now have very few to none high pitch't tones.
Conclusion? Breathe! I really can't stress enough how important it is and how many benefits you can reap by starting today. You will feel a deeper breathe since the very first attempt try and just make a long sound like a " La " with the usual chest breathing and one with the Diaphragm and see which one is the longest.
I hope you find this useful and make it a part of your life if you haven't done so already.
Good luck in your journey and Take Care!