I see this "acting" just about every time I talk to someone, or overhear others talking. Sad, but it is the way of life. Everybody's trying to present the illusion that their somebody they're not. It's like people are embarassed to show others who they really are.
As for relationships....I don't see the point of being with someone long-term that you can't be yourself around. If you can't talk to them as freely as you would talk to your best friend(assuming that they really are a best friend), then it's not worth the trouble. Unless, you're just playing the game for sex, then that's a different story, and it's short-term.
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Those who speak, don't know.
Those who know, don't speak.