Re: Exercises to keep breathing?
One of my teachers recommends turning off the hot water at the end of a shower and trying to control your breathing through the shock of having cold water spray on you. (This is the "home version" of cold-water misogi.) He says that if you can learn to control your breathing through that, it will carry over into ukemi. You can ki-ai on the exhale to make it easier.
I will admit, I don't do this very often, and usually end up springing out of the shower as if poked by a pin....