ways my T has suggested to me to stay grounded are repeating a mantra of your age the year and that im safe over and over out loud if needed or in my head to get me back into the present when im reliving in an alter the traumatic past and it does help takes time though
another way is to have something to hold onto that you have from a happy time or the present that u can use to bring u to when u got that and associate with the memories of that object which can be anything
-i dont really use this second one cos i never really could find anything to help but thats just me...