Originally people said things like, “I was so delighted with the wrapping that I couldn’t bring myself to open the package.” But then they began to lazily say “You made me so happy,” no longer explaining just how happy that was. This pattern of using “so” as a simple intensifier meaning “very” is now standard in casual speech, but is out of place in formal writing, where “very” or another intensifier works better. Without vocal emphasis, the “so” conveys little in print.
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