Leaves on a stream is a technique used in acceptance and commitment therapy (ACT) to cope with uncomfortable thoughts and feelings. This technique uses a concept called cognitive defusion, which works by creating distance and disconnecting from thoughts and feelings, as a way to reduce the power they have over us. 

During leaves on a stream, you will practice cognitive defusion by clearing your mind and visualizing a stream. Whenever a thought enters your mind, you will briefly observe it, place it upon a leaf, and watch as it floats down the stream.