I always try to do grounding exercises that remind me I'm part of the world and it's not just a dream. Whether that's touching different textures or talking to another person. It's important to reconnect yourself. It's also important to accept that your dissociation doesn't make you any different, and to remember that even if it doesn't feel like it you are real and people see you. I like to write down how dissociation feels to me, that helps me process the experience better so I feel better prepared for when it happens again. These are things that sometimes help me so maybe they'll help you :)