Smile doesn't cost a cent.

微笑不用花费分文。

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The bottom line is that a smile doesn't cost anything and may do you good.

不管怎么说，微笑不需要任何成本，却对你有好处。

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Whenever we smile, nerves and muscles may transmit messages that turn on happiness centers in the brain, Laird speculates. "The bottom line is that a smile doesn't cost anything and may do you good."

拉瑞德推测，无论何时我们微笑，神经和肌肉会传送打开大脑中快乐中心的信息，“结果是一个微笑不花费任何成本而可以使你感觉良好。”

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