Imagine a frog that is swimming in a vessel of water. Someone lights a fire underneath the vessel and the water starts heating. As the temperature of the water rises, the frog is able to adjust its body temperature accordingly. The frog keeps on adjusting with increase in temperature, even when it starts to feel less comfortable.

Just when the water is about to reach boiling point, the frog is not able to adjust anymore. At that point the frog decides to jump out. The frog tries to jump but is unable to do so, because it lost all its strength in adjusting to the water temperature. The frog is no longer able to save itself and starts cooking and dies. 

Had the same frog been thrown into warm water directly, it would have had the strength and intuition to jump out and save itself. What caused the death of the frog? Not the boiling water but it’s inability of recognising a dangerous situation sooner. This is an illustration of how we sometimes grow accustomed to situations that are unhealthy for us and we gradually get used to an unhealthy situation. We lose our strength and our ability to get out of a toxic situation without being harmed.