Both? Remembering to BREATHE is a very helpful technique for centering or grounding whichever you call it. Feeling your breath helps to know you're alive and not be so ethereal about the situation and events going on around you.

Often when we begin to lose touch with our surroundings --dissociate-- we fail to breathe deeply enough. This affects our brains for sure, but also our muscles which can then begin to feel numb and "unreal" also.