Why can we share negative happenstance (break-up, rape, abuse, etc.) pore readily than positive?

if something bad happens we all run out and tell our best friend, our date, our family, whoever. we moan and gripe about it. but then you have a fantastic day at work, a great conversation with a friend and its topped off by a romantic (or perverted if you're like me ;%26gt; ) night with your sig. other and when people ask about that day we say ';it was good. and leave it?Why can we share negative happenstance (break-up, rape, abuse, etc.) pore readily than positive?
It helps to share and release stress.

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