It seems that when we understand our feelings on a rational, emotionless, level, they dissipate. In this way, talking about our worries makes them go away, but even analysing them rationally ourselves, with writing, poetry or logic often dissipates them. So, it appears that emotions are messages to be acted on, but these appear in an abstracted form, so it's not always obvious what the message is, or not always possible to act on it. Once the message is read, understood, acknowledged, it vanishes.
We can assume that this also occurs with positive emotions too, that a happy impulse is also a message. This implies that understanding our happiness would make it vanish. Perhaps nihilistic feelings come from analysing happiness. To retain positive feelings then, it is best not to act on them, or analyse them, merely ignore them.
Understanding the feelings of others may have the same positive effect on ourselves, but of course not on them.
Perhaps the essense of evocative art is to create a feeling in us, then explain it and thus dissipate it. Perhaps in arts such as poetry, the evocation and the explanation occur in one.