I think breath should be the first line of defense against dissociation. Breath is a common thread in so many more complex practices and is widely recognized as a parasympathetic system activator. In yoga, meditation, therapy, and other practices that I did not include above, breath is taught as an integral part. In some waysmy conclusion is already recognized in the mainstream, whenever someone starts to show signs of distress, the generic response is often "take a deep breath." Breath is also so easy to implement in your daily life. Requiring no tools or prior experience, making this instinctual bodily function intentional can do wonders to ground you.

That being said, everyone’s bodies are different so there is no perfect answer. What may work for me may not work for you. For example, cutting caffeine was a vital step for me in order to get more grounded, but less caffeine sensitive people can continue to use caffeine to wake them up for the day without a consequence of the acute stress response.

Furthermore, it is likely a combination of a couple of these methods and even ones I did not research that will help you live a more grounded life. When trying to find the perfect combination for you, first try the things that work best for your schedule. As wonderful as any given technique may be, if it is not sustainable with your lifestle or accessible when you need it, then it is not the practice for you. As someone who has tried most of these techniques, there is not a cure-all for grounding. Nevertheless, I hope you try some of these the next time you are overwhelmed and dial in to your life. 

Best of luck to you!