Practicing mindfulness helps to come back in the now moment, to calm anxiety and panic attacks, it helps us on the path to self-mastery.
Here is a list of tips you can use in case of anxiety or anytime you want to take a (mental) break:
focus on your breathing, feel the air coming in from your nostrils or your mouth as you inhale and feel it coming out as you exhale, become aware of the movement of your ribs and your belly
focus on your physical senses: what you can see around you, what you can hear, what you can feel with your hands, what you can smell...
notice the contact points of your body, ex: if you are sitting, the contact of your body on your seat, your feet on the ground, etc. and see that you are safe
take a mental break, notice your thoughts and decide to let go of any thoughts that you are considering as negative or harmful
don't imagine negative scenarios
focus on your actions and tasks, on what you are doing concretely at this very moment without thinking about the past or the future
see that in the now moment, all is ok and you got this...