It's the little things that can make a difference to a performance: the way you flick your right hand out whenever you're reaching for a high note, the fact you swing your arm ever so slightly when you sing or the stance you adopt when you're listening to other characters on stage.
It's so intrinsic to helping you relax that you don't even notice - until a director points it out and you're suddenly aware of how distracting to an audience it might be. Those are the times when you must step outside your comfort zone and into character.
Just ask Keshia Tunks.
Back in 2005, Tunks - then Keisha Paulse - was a New Zealand Idol finalist on her way to a singing career that would include writing her own songs, appearing in musical theatre productions and performing with bands around the world.
Then she took a break, studying for a Bachelor of Youth Development, getting married (to fellow musician Karlos Tunks) and, this year, welcoming a child. At the beginning of 2017, surrounded by nappies, the last thing on her mind was stepping out of her comfort zone to play the lead in one of her all-time favourite musicals.
Now, thanks to a good word from former NZ Idol judge Jackie Clarke, she's Deloris Van Cartier in Sister Act, the Musical. It's a role made famous by Whoopi Goldberg in the 1992 film where Deloris, a wannabe diva, sees her life take a surprising turn when she witnesses a crime and the cops hide her in the last place anyone would think to look: a convent.
Tunks reckons she's watched the movie thousands of times.
"The nightclub scene was my favourite because we were a church family - that's where I started singing - and anything like that was so far removed from my reality," she says. "I kind of feel like Deloris is my alter ego. In the musical, we see more of her sexy and sassy side, whereas in the film she's more comic but, yes, you have to be careful that it doesn't all become a parody."
Sitting in the foyer of Auckland's ASB Waterfront Theatre, Tunks seems almost bemused that it's happened. She says she was just happy to have been given an audition. When she got the role, family and friends stepped up to help with childcare.
"I'm terrified! But it's that good excitement ... "
She's also grateful to director David Adkins for pointing out that she does hold her right hand on an angle when she sings. It means training herself out of the habits, developed during the course of a decade spent doing her own thing.
"I haven't done musical theatre for about eight or nine years so I do feel like a bit of an imposter but, you know, to grow you have to go through that 'yucky phase' but my brain is like a sponge at the moment, soaking it all up."
If it's an unexpected change for Tunks, it's also a new experience - of sorts - for co-star Matthew Cutts. After 25 years of performing in London's West End - in the likes of Cats, Miss Saigon, Starlight Express, Jersey Boys, Mamma Mia, Grease - the former Greenhithe resident is back in Auckland.
When Brexit happened he and his wife decided it was time to live in NZ. Friends gave his name to Amici Productions, the company producing Sister Act in NZ and he landed the role of Deloris' gangster boyfriend, Shank.
Because Amici uses casts made up of paid professionals and keen community theatre performers, Cutts says it's been a long time since he worked alongside people doing something simply for the love of theatre.
What: Sister Act, the musical
Where and when: ASB Waterfront Theatre, November 25- December 16