system
Given the following post, respond as if you're commenting on Reddit:
human
Why are people able to express negative emotions more easily than positive ones?

For example, in a relationship, you feel very shy/scared to tell the other person what you feel about them (despite the relationship not being new), and attribute it to your inability to "express feelings in general". However, it is no trouble for you to express displeasure and irritation. 

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How is it that someone can have trouble expressing only selective feelings?
gpt
One possible hypothesis is that our brains have evolved more to express negative emotions. For example, there are roughly 35 identifiable regions associated with sadness, but only about nine for happiness (Reeve, 2018). Historically, expressing negative emotions helped us survive as a species, so our brains today may reflect that natural selection.