Visible, felt change often starts with the invisible stuff that's beyond our everyday perception and awareness. So growth is about expanding our perception and understanding of how complex systems actually work, because human beings are indeed very complex systems.
There is still so much we don't know about ourselves, our inner and outer workings. And not knowing is somewhat of a good thing; it's actually an antidote to despair, because it means there are possibilities that exist that we do not yet know about (not all unknown unknowns are bad).
I remember being taught that the body is 70% water. But I was never taught that microbial cells (such as bacteria, viruses, and fungi) on or inside my body slightly outnumber the cells that make up my body. The Human Genome Project to sequence and map all human genes (the genome) began 1 October 1990 and took 13 years. The Human Microbiome Project to analyze and understand the role the human microbiota plays in our health only began in 2007 (here's a primer on our microbiome), so we're still in the very early stages of unraveling this mystery. But that hasn't prevented a whole host of biotech companies from popping up that make all kinds of health promises based on flimsy findings (many involve analyzing your poop).
If you want to have your mind blown, read Ed Yong's I Contain Multitudes: The Microbes Within Us, The Grander View of Life or watch his 2018 talk at Mind Science Foundation below, where he warns us against jumping to sweeping conclusions and embracing simple solutions (such as taking probiotics) based on early-stages of research.
But here are just a few things to ponder:
Diet -- We've been told many times that "we are what we eat", but we're discovering that the mind-gut connection flows both ways. What we crave conveys important information about our current state, while what we actually feed ourselves can also impact how we feel. So examining and optimizing our diet is a good place to begin experimenting on ourselves. A simple way is to start is with an audit of our alcohol, sugar, and processed food intake. Then cut the highest one for 10 days and observe any changes to energy, sleep, mood, and body composition. Rinse and repeat for the other two. This article has more on improving gut health and the possible links between diet, depression, and inflammatory diseases (again, emphasis on possible and we aren't sure about the direction of the link).
Environment -- In his book, Yong cites research (such as this and this) that suggests possible links between higher incidences of food allergies, asthma, and inflammatory diseases and environmental factors common in developed countries: Yong points out that benevolent microbes "have been a part of our lives throughout evolutionary history, but their tenure has become shakier of late." He goes on to explain that it's not just better hygiene practices, "it’s also due to the various trappings of urbanisation: smaller families; a move from muddy countryside to concrete cities; a preference for chlorinated water and sanitised food; and a growing distance from livestock, pets and other animals."* Homes with cats and especially dogs have been shown to have a more diverse range of microbes that help "train" our immune systems not to overreact to non-threats. This begs the question of whether there might be long-term/second order consequences from the constant use of hand sanitizer during our current pandemic. And we should not lose focus of the fact that not only have we coexisted peacefully with most microbes, they have also brought us life-supporting benefits. But whether a microbe is helpful or harmful to us can depend on the particular circumstances of the moment; nothing is fixed, everything must constantly adapt. The more changes we make to our environment, the more we, and everything else in it, will have to adapt. Everything has to adapt to each others' adaptations to achieve a new equilibrium.
"We're multispecies beings" is how Wendy Garrett, professor of immunology and infectious diseases at the Harvard T. H. Chan School of Public Health, describes us. Let the implications and all the questions that arise from this explosive view of ourselves sink in. We are so much more than what we've been told or what we think we are, which means that the possibilities of what we can be are also more than we can currently imagine.
*Yong, Ed. I Contain Multitudes (p. 122). Ecco. Kindle Edition.