Take a deep breath in through your nose, let your stomach out and your chest swell. Now let it all out through your mouth.
When was the last time you did that?
We get so focused on whatever we're working on or thinking about that sometimes we forget to breathe. I don't mean literally, I hope you don't pass out on a regular basis, but in the sense that short shallow breaths with a clenched stomach isn't really breathing.
Now we have different types of breath for different situations and we shouldn't always be deep breathing. But a few more deep breaths a day will probably lead to a few less gray hairs. (In my scientific opinion...)