A random thought while flying across the Atlantic: Is the etymology of "Don't sweat the small stuff" nautical? I can't find anything on this anywhere, other than this charming thread which quickly devolves into petty forum bickering.

Anyway, for the uninitiated: "Small stuff" is any kind of thin rope or twin that wouldn't be suitable as lines on a boat. Think sewing thread. I imagine you'd use "small stuff" for miscellaneous sewing and maybe whipping a frayed rope. And to "sweat" a line is to pull its slack. That's what dictionaries and wikipedia say, anyway, though to me "sweating" is a more specific term which means specifically to pull a line orthogonal to itself, which is part of a two-person maneuver to pull in a line under tension. Maybe the latter term evolved from the former, a sort of semantic circumscription. In any case, "sweating" is the kind of thing you do when you really need to, and it involves putting a lot of force on the line.

In other words, "Don't sweat the small stuff" could have once meant "Don't pull really fucking hard on a little piece of twine." It's original meaning could've been very practical and literal: Don't weat the small stuff, because not only is it not necessary, but you're bound to snap it!

Between that literal meaning and the current one of "I can't be worried about that shit. Life goes on, man!", I can imagine a sort of intermediate meaning, which would be something like: Don't force things that need a gentle touch; you're more likely to do harm than good.