The out breath helps to calm all the body, functions and systems, down so it makes sence to develope personal stratagies to slow it down.
Heres how breathe in, through your nose, and as you breathe out, through your nose, make it longer and slower.
Feel it don't force it
Breathe in and slowly count , breathe out and count at the same pace but make sure its longer.
Repeat five times, every hour.