"There's something when you're not feeling very strong, where you push yourself."
However, she said that her upcoming roles in Eternals and Maleficent has given her a much-needed push back in the right direction.
"I'm so grateful that I have the opportunity to play these kind of characters, that pull out every bit of strength I have and that remind me that I can be strong.
"Sometimes you really feel low and you gotta pull it back up."
Jolie graced the red carpet at Disney's D23 Expo on Saturday night, wearing a stunning black dress while promoting the sequel Maleficent: Mistress Of Evil and her anticipated role as Thena in Marvel's Eternals.
Her character is a superhuman with exceptional strength, stamina, speed, reflexes and durability.
Eternals is set a million years ago and is expected to have a completely different look to the Avengers series.
Speaking about her role, Jolie said: "Right now, for Thena, I'm having to do so much training and she's so positive, so healthy and she's so aggressive that I'm often like, 'This is not gonna work'. But, you gotta push yourself."