The 30-year-old said that she is "afraid" of what lies ahead after seeing her profile rise in the past year with roles in The Tree of Life, The Help and Coriolanus.
"This has been a scary year... a wonderful year," she told AnOther Magazine. "But my life is changing and I don't know what it means. All year I've been afraid of falling flat on my face, physically and metaphorically.
"'I'm not talking about the fame. But I knew I was going to be an actor... I would be really happy doing plays off Broadway for hardly any money."
Chastain also said that she doesn't consider herself to be a sex symbol.
"I'm not the normal idea of what a gorgeous woman is. I don't look modern," she insisted. "There's nothing about me that makes you think, 'movie star'. I'm just this normal girl."
Chastain was recently linked to the Princess Diana biopic Caught in Flight, but Naomi Watts was ultimately confirmed for the role earlier this week.
> Jessica Chastain: "I love that people don't know me"
Watch Jessica Chastain in the trailer for Take Shelter below: