A lot of actress can rely solely on mechanics to withdraw feelings/emotions from their audience. It's a talent that's not restricted to this "all my life, had to fight" process you're referring to. I'm not saying using real emotion when you perform isn't effective, but it's not the only way. Though, going that route sometimes causes viewers to disconnect from what they're seeing because it might be too uncomfortable to watch or it'll take them out--and that makes the performance totally ineffective.
Bey uses her training to make the gorls feel and that's fckin that.