Many of us these days experience some pretty intense emotions when we’re in some very passive states: Our hearts race as we for the well-being of a fictional character on a movie screen, while we sit back and watch from a cushioned seat; or we marinate and stew for hours in powerful feelings of longing or while we lie motionless on our couches.

Our emotions, however, were designed and fine-tuned by evolution largely to prepare us for action, for movement — to alert us to our true situation and help guide choices that ultimately must become physical choices.

Whenever an emotion is triggered in us, our bodies are instantly and unconsciously affected in very specific ways. When we experience the emotion of disgust, for example, our eyes tend to narrow, our mouths to shut tightly, and our bodies to move away from the object of disgust. Disgust is typically triggered, again unconsciously, by something or someone that may pose an immediate health risk to us — such as rotting meat, which may contain dangerous parasites, or, for example, by a person coming towards us who has open, festering sores, and who may, therefore, transmit to us a potentially dangerous infection or disease.

To be healthy and functional, we need to be able to feel and connect to all of our emotions at different times, even to the less pleasant ones. If you’ve just crossed the street in an unfamiliar neighborhood, for example, and see a group of large men down the block playing with switchblades, you may feel some trepidation, some fear at a visceral level. Good! You need that fear to help you make good choices — like, in this case, perhaps walking on a different street.

Studies have shown that when animals are incapable of feeling fear, they don’t survive for very long, and the same is undoubtedly true for people. Of course, most people in modern life, as we’ll discuss later, have far too much fear in their lives rather than too little, and this excess fear can be extremely destructive and crippling. But we do need the capacity to feel fear, just as we need the capacity to feel all of our other negative emotions, in certain circumstances.

Biologically and evolutionarily, all “negative,” or distressing, emotions, like fear, disgust, or , can be thought of as “survival-mode” emotions: They signal to the body and brain that our survival and well-being may be at risk, and are specifically designed to motivate behaviors and bodily responses that can most effectively deal with those risks and threats.

Survival-mode states can be said to biologically oppose states of “homeostasis,” which are states of physical and psychological balance. In a state of homeostasis, we sense or perceive no pressing survival-related needs, such as a hunger for food, and no apparent survival-related threats, such as people flourishing knives in our vicinity. When we’re in homeostasis, that is, we feel physically and emotionally safe.

In general, when we’re in homeostasis we tend to experience positive emotions and feelings, like joy or love, and when we’re in survival mode we tend to experience negative or distressing emotions and feelings. Indeed, the activation of a negative emotion like fear is precisely what throws our brains and bodies out of balance, into non-homeostasis or survival mode. As unpleasant as some emotions can be, however, every type of negative emotion that we experience is evolutionarily designed to serve one overriding purpose: to help motivate behavior that will bring us back into homeostasis. Homeostasis is where our bodies and brains want us to be whenever possible.

To give another example, when the levels of various nutrients and minerals in the cells of our bodies start to drop below a critical point, those cells begin to veer dangerously away from homeostasis, and a signal is sent to our brains that creates a hunger for food, which amounts to an emotional state of hunger. And we don’t just feel hunger with our brains — our whole bodies, in effect, become hungry, and that state of hunger will drive us to find food however we can. Once we’ve eaten, particularly if we eat natural, healthy food, the nutrients in our cells will be replenished and we can come back into homeostasis — not only at a cellular, physiological level but also at a psychological, emotional level.

Negative emotions like hunger, fear, or disgust, therefore, serve what could be called the “homeostatic drive” within us — an extremely powerful and all-encompassing force that has been crafted and honed by evolution to keep us in homeostasis whenever possible, and to return us to homeostasis when our balance or equilibrium has been disturbed.

In our previous hypothetical scenario, fear served the homeostatic drive by motivating you to avoid a street with knife-wielding men and instead to walk on another, let’s say more pleasant, street — perhaps a street filled with trees, puppies, and cute children. That sounds safe and homeostatic enough. But let’s say that as you walk along this tree-lined street you see a small boy pull out a water pistol. Let’s further say that a long time ago you were robbed at gunpoint, and that since then, you’ve been so skittish about guns that even the sight of a water pistol creates a potent and lingering state of fear in you.

This fear will inevitably become visceral — not only your brain, but your whole body will, in effect, become afraid. Your body will likely become noticeably rigid, triggered into survival mode, and yet at the same time part of you will realize that this fear that has “frozen” your body makes no rational sense. Part of you knows there is no real danger from a water pistol, and yet another part of you is afraid — but only because the fear is being triggered by the of your old . So the more sensible, rational, healthy part of you is not aligned with, is disconnected from, the part of you that is throwing your body unnecessarily and inappropriately into survival mode.

All disconnection between the brain and body, we could say, is some version of this same dynamic: it happens when the body, because of various cues or triggers, is thrown into an unnecessary state of survival mode that does not correspond to any actual or significant risk to survival or well-being. In modern life, this kind of disconnection is remarkably, shockingly, and tragically common.

And, unfortunately, this core, fundamental disconnection between the brain and the body, this unnecessary intrusion and imposition of survival mode, will inevitably lead to more disconnection, including, as we’ll see in future posts, disconnections between what you actually do and what you truly care about, and between you and the other people you care about. Once a core disconnection develops between the brain and the body, the homeostatic drive has to constantly fight against that disconnection — the signals and motivations that the homeostatic drive tries to supply will often become, so to speak, jammed, misrouted, and misinterpreted, typically to extremely unfortunate effect.

But if unnecessary states of survival mode are ultimately what create these destructive disconnections in our lives, what is it that generates so much survival mode? Why do survival-mode states intrude on our lives so frequently and so forcefully, ruining our fun, damaging our relationships, and often leaving terrible destruction and misery in their wake? We’ll talk about this more in the next post.