To be homeothermic means to maintain your normal internal body temperature regardless of the external temperature. One advantage of being homeothermic is that it enables you to exercise when it's cold outside because even as your body internally heats up, you sweat to release all that built-up heat and energy.
This is a case where a memory so strong affects your current mood. It is related to those unsolved or unspoken things as well. The state-dependent memory. This happens when the current state of the person is simmilar to the state that she or he had when the memory had initially formed.
In this example, Jackie is recalling the times Andy kept things hidden from her, which triggers the memories of him having lunch with the former girlfriend and, all of this, ends up with her withdrawing from Andy.