Leaves on a stream is an Acceptance and Committment Therapy (ACT) exercise to help with distancing and observing thoughts. It's a useful practice to learn to help you deal with intrusive cognitions and to help you deal more effectively with triggers, stress or anxiety.
 
You can listen at any time of the day to suit you.
 
It runs at 15 minutes so settle down, pop those headphones in and enjoy this deep relaxation. Never listen whilst driving.