To prepare you for meditation or if you feel nervous. You can do it anywhere and anytime.

Start by observing you breathing. Let it flow naturally.

Then while inhaling say calmly in your mind “There’s only this moment” and

while breathing out “and in this moment peace”
Focus fully on this chanting in your mind.
Breathe in the rhythm of this chanting. Observe how it starts to slow down and calm the mind.

Repeat as long as you like or until it stops naturally.