"The toughest part is that when your kid's upset, you're upset. You're rocked until they're not upset. Even when they're not upset, you're like, "I hope that doesn't happen, down the line." You're always nervous because you want your kid to be happy."

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However, perhaps the main point is that you are under no obligation to analyse variance into its parts if it does not come apart easily, and its unwillingness to do so naturally indicates that one's line of approach is not very fruitful.

— Ronald Fisher