"How are you?"
"I'm good," you reply.
"You're good? No, you're not! You're well!" says the smug friend whom everyone hates.
Before you grumble a halfhearted apology for being an ungrammatical nitwit, stop yourself. Because -- get ready for a breakthrough -- you are good.
The long-held myth was that you should use an adverb (such as "well") to describe how you're doing. But most of us get that "am" is a form of the linking verb "to be" (I am, she is, you are), so we can use an adjective for description. You don't need to say, for instance, "I'm busily" when you're trying to finish your crossword in record time and your kid is asking for a snack.
In other words, using an adjective is perfectly acceptable, and "well" is -- in fact -- used in adjective form when we say "I'm well." Also not worth hearing? The argument that "good" can only apply to our moral character and that "well" means we're physically OK. That's just a matter of usage. We all commonly accept that "good" can mean "well." You're good. You're well. We're all fine.