Homeostasis is a set-point which your body creates, in response to your behaviours, so that you know when you feel normal or not.
Good News: There are many possible homeostatic points. Your challenge is to find one that is healthy, rather than to live in an unhealthy way.
Homeostasis in the Body
Your body tells you what it "needs." You know when you need to eat, or drink, and you have cravings for foods that supply the nutriments that you need.
Several studies have shown, that young children given a wide variety of foodstuffs to eat from, and freedom of choice, choose a diet that's surprisingly good, in terms of nutritional needs.
Homeostasis controls your body temperature, your weight, your blood sugars, the amount of cholesterol in your system, when you feel sleepy, your desire to exercise; - almost everything you do, is affected.
When your homeostatic system is itself "healthy" it will help you to be healthy too. But because of our personal behaviours, or because of social behaviours we adopt, we can force our homeostatic system to find another "set point" that is not so healthy.
Control of Body Cells
All the cells in your body are under control. That control is from the signalling of other surrounding cells. Every cell requires "You're OK" signals from surrounding cells to continue to "live."
In the absence of "You're OK" signals; cells are programmed to switch themselves off. This process is called apoptosis. It's a process active in your body everyday.
Homeostasis is another example of this sort of control, with the signalling system being hormones and enzymes, linked into the nervous system as well. It's a whole body system; it can't be understood by looking at disassembled parts.
Your Body Adapts to Your Behaviour or Circumstances
Your body tries to find a way to cope with your behaviours, and makes the best adaptation between that behaviour, and the needs of your body.
We know that the body adapts to excessive alcohol use, drug abuse, over-eating, obsessive exercise, and to chronic pain.
The body also adapts to traumatic experiences, like child abuse, or repeated violence or warfare.
Prisoners kept in isolation, slaves, many women in abusive relationships, develop a delusional self-protective mental state, that makes them feel safe, yet reinforces their entrapment. That too becomes part of adaptive homeostasis.