OK, then, if we don't really want people to be themselves, what are we trying to get them to do? Maybe the advice should read something a little closer to this: "Find and develop your unique potential for doing good in the world." This is very different from "be yourself." It's closer to "be the best version of yourself." Of course, this variation brings its own challenges: what does it mean to be the best version of yourself? How do you determine what "best" is? Is it the version that brings the most personal comfort? Is "best" a synonym or an antonym for "most authentic"? And for that matter, is personal authenticity the most important thing, and who determines what that looks like?
I'm still mulling over some of these questions, and I probably will be for some time if not the rest of my life, but here's what I've sketched out so far: the best version of yourself probably requires some effort to achieve, though not Herculean effort. It's the repetitive, daily activity of taking a hard look at your own behavior, monitoring how closely your choices reflect your ethical beliefs, and making adjustments so that your actions hew to your ethics as closely as is practicable. It may not be comfortable, in the sense that it hardly fosters feelings of complacency, but it probably creates a long-term sense of inner peace, since you don't have to live with constant nagging feelings of hypocrisy or cognitive dissonance. Being the best version of yourself also involves discovering your particular talent -- something you can do well that's beneficial both to you and to others -- and honing that talent through practice and education until it shines.
Any additional thoughts about being one's best self? Or have you noticed any other affirmative advice that seems kind of sketchy on second glance?