How often have you found yourself attached to something, someone, an emotion, an experience? Have you observed your reaction to the attachment? We re-play an event; we obsess over what will happen if we don't have an object; we wonder what we could have done differently in a relationship and the list goes on.
The act of letting go of attachment to the senses; to events and emotions we link to the concept of pratyahara in yoga. We learn to let go and assume control of our reactions. Nobody else can do that-that power resides within us.
I come back to the saying "the mind is the master of the senses, but the breath is the master of the mind." When we learn to breathe; to be; we begin to tune in to our reactions and then learn to let that sh*t go.