Here is a simple exercise of using your breath to return to the present moment.
Wherever you are and whatever you do, bring your awareness back to your breathing
Close your eyes, or just or just soften your gaze and take a couple of intentionally deep breaths. Observe the sensations caused by the inhalation and the exhalation – the rising and falling of the belly, the expansion and contraction of the chest, subtle tickling in and around your nose, or anything else you might notice.
As thoughts start coming to your mind, do not develop them further. Recognize that your attention has been pulled away from the breath by your thought, then gently return your attention to your breath and let the taught pass.
Stay with the breath for as long time as you can spare, and a few breaths more, and then return to your daily activities with a calmer mind.
And for those moments when you feel that you really have no time, or patience, or focus to stay with the breath even for a minute, try doing the following: take one deep breath in, observe it. Exhale completely, observe it. Then take one natural breath, observe it. For the duration of these two breaths, try to disengage from anything that is happening around you as well as from all mental chatter going on inside your head. For two breaths stay out of it all and observe the world within and without as if you were watching a movie. Practice this whenever you remember it. You will be surprised to see that even only two fully conscious breaths at a time can make so much difference.