Being one's self, whatever that means

The other night I broke and reverted to North American English--the accent, the expressions, everything. At once, I wanted to speak and speak and speak. Rick and Jacquelyn, across the table from me, listened. Behind them were the balcony's sliding doors, made of glass. In the glass, I could see myself reflected. I was smiling and glowing from the pleasure of speech.

"What's different?" Jacquelyn asked.

"I'm not hindered," I said.

Then Rick and Jacquelyn told a story of a British woman raised in Argentina by her missionary parents. The woman was prim and proper in English, but relaxed and animated in Spanish. At a party dominated by Spanish-speakers, the woman told stories filled with emotion and punctuated by gestures. On the car ride home, among English-speakers, the woman straightened her spine, put her hands in her lap, and within twenty minutes morphed back into her usual English self.

A natural question: In different languages, are we different people?