Jon Aaron offers this easy mindfulness-based breathing exercise that can soothe and center you. "It could be expanded to an hour," he says. Use it daily as a practice so it's ready in moments of extreme stress.
During the first minute, stop and notice what's present in the mind, what the mind state is, what the mood of the mind is, what the emotions are.
The next minute, check in with the body. Notice what's felt in the body, what sensations are present, where tension might be held.
Next minute, come to your breath, allowing awareness to be with the sensation of breath without having to control the breath—just sitting there with this awareness of the body breathing.
Then get back to handling your day, because you can!