Your body is a house full of thermostats.
Homeostasis is your body's core principle: for every important variable there is a set point, a sensor and a counterforce. Temperature around 37 degrees, blood pH at 7.4, blood sugar around 5 millimoles per litre. When a value drifts, a counter-reaction starts until it is back. Almost everything you know as a symptom, shivering, thirst, sweating, is one of these controllers at work.
Useful: With every body signal, ask: which set point is the body trying to hold right now?
Source: en.wikipedia.org