We're all taught that being mindful is good for us. Any type of meditation will reduce anxiety and lower cortisol levels. Simply taking a few deep breaths engages the Vagus nerve which is usually on fire in stressful scenarios.
However, being mindful is useless unless you create space. What I mean is space = intention + focus to direct your thoughts on only one subject/object. You can be mindful sitting in the car in traffic and create space for_____ to happen and make room for decompression. In your space, focus on the sound of your breath, or focus on what you are smelling. These two senses really dominate our experience and can slooow down the rapid fire vagus-cortisol expression.
Waiting for the absolute quite time is ideal and makes it easier to create space, but when you don't have the luxury, this is a quick & easy way to center yourself. When you take your mind off of the stress topic or event that occurred that got you fired up, it triggers a signal within your nervous system to slow heart rate, lower blood pressure and decrease cortisol.