The thing about depersonalization/derealization is that they are coping mechanisms because our brains are overwhelmed with reality (whether it's our external or internal reality, that's a different question). I've learned to just accept that that is what my mind feels it needs to do to protect itself right now and try not to panic when it's happening, and sometimes that's all it takes to ground myself. Sometimes not, but it does alleviate a bit of the eerie/perturbed feeling.

But if you're recognizing it, that's half the battle, and that's huge.