Equilibrium can refer to balance, but also to different states being equalized. For instance, the cabin pressure of an aircraft is much greater when cruising at altitude than the air outside, where the air is too thin to breathe. Although the Earth’s atmosphere is about 300 miles high, most of the air is in the lowest few thousand feet closest to the surface. In fact, there are 14.7 pounds per square inch of pressure in the atmosphere at sea level, which allows us to breathe normally. As the aircraft descends, the difference between the cabin and atmospheric pressure outside becomes equalized; so that when we exit the aircraft, we don’t notice the difference.
Other examples of managing the equilibrium of different environments are when divers need to take decompression stops as they ascend from depth and space-walking astronauts who spend a day in an airlock chamber acclimatizing their bodies, before opening the door and walking in space.
Similarly, we can all experience internal pressure when we’re feeling stressed or anxious. This can be through physical tension and muscle tightness in our body, restless thoughts in our mind, and unsettling feelings.