Extreme Emotion
When we get stuck with a single state of mind where anything else becomes irrelevant. It is that state of mind.
Sometimes listening to a melodious song we get engrossed in it. Such that we cut off from the external environment.
Past memories which stay with us for a long time and we tend to remember them even after so many years. It is due to our extreme emotions that we are associated with that memory.
Extreme emotions can be sad at the same time it can be happy too. Emotional behaviour can arise due to something which is close to our heart or something for which we long for and we get that!