As the human we have wonderful power, to bring & relive the happy moment in the past in our mind or to overthink any fearful/hurting Situation over and over again.
The effect of these two thinking is different. When you think of a happy or funny moment, it surprisingly lost its fun part after some time. But when you think of fearful/hurting situation we add our imagination and think what if it happened like this, what if anyone thought like this. we ourselves make it big, unknowingly with our thinking alone. Otherwise, it’s fairly simple emotion Happiness, Fear or tragic. Agree?