Whenever you are feeling out of sorts in anyway, the first solution anyone offers is take a deep breath.
When undertaking any task, one tends to draw a big breath at the beginning of the task, and breathe out when the task is completed. When undergoing a possibly painful medical or dental procedure, you are told to breathe deep.
Drawing a deep breath seems to reset mind and body. It has the ability to wash away fear and stop time. Inspiring words and music are carried out on a carpet of breath. The key to this to be aware of your breath.
Control it with a mantra, or simply time your breath by counting as you inhale and exhale. So it does appear that it really is that simple, just keep breathing.
That's easy enough to do in your sleep.