What do people mean when they say "just be yourself"?

[Mona Realm]

The other night I said on twitter I'm in a bit of a sassy mood so I'll log off.(something exciting happened that night) a friend of mine says "haha yes you are but just be yourself." I said "Thanks! I like being yourself."

Why do they say be yourself when you already are?? Is it like saying "don't be ashamed of your sassy side be yourself"??
there are occasions where I get sassy or excited. depends on what happened
I meant "thanks I like being MYSELF"

[David Wang]

It means that you can be the way you usually are, and not any other mood, tone, etc.

[Mutechords]

means do not change your looks/likes for making other people happy

[Mr. Perfectionist]

They meant you didn't have to log off just because you were feeling sassy, if that's how you feel continue; you shouldn't censor, or limit yourself just because You feel others will say something. I like sassy it shows confidence, and individualism.

[adeline_cosine]

"Sassy" is good! It means fun, unpredictable, and not afraid to stand up to others. "Just be yourself" I interpret the same way as you -- as telling people that they should like themselves the way they are and not to worry about trying to act like someone else.

I think you were complimented both ways!