The one thing that you do automatically, without thinking, is breathing.  Mindful breathing is when we take manual control of our breath.

It follows like this:

INHALE (for a count of 5)…. HOLD (for a count of 5), EXHALE (for a count of 5) repeat this 5 times

This exercise should take around half a minute to perform.    Try to breath in, past your chest and into your tummy, and solely focus on this one, vitally important task.