Reese Witherspoon was "not a grown up" when she married Ryan Phillippe

Reese - who was married to Ryan for eight years and went on to wed Jim Toth in 2011 - said: "I got married when I was 23 years old and you're not a grown-up at 23. You think you are, but you're not.

"Then your life suddenly changes and I love that this movie explores that, as well as the next chapter and how you have to decide whether the track you are on is where toy want to be for the rest of your life.

"I think that's what a lot of women in their 40s are trying to figure out."

These days, Reese - who also has five-year-old Tennessee with Jim - couldn't be happier with where she is in her life.

She said: "I feel great. It feels like a time when you know who you are, what you want to accomplish in life, and you have all this knowledge and experience to share with people.

"I think this movie shows that we all have to find ourselves and be OK with ourselves no matter what happens."

The 'Big Little Lies' star is an avid user of Instagram but admits she has an ulterior motive for using the social media site.

She explained to Britain's HELLO! magazine: "I actually learnt about social media through my kids and I think it's important to follow them and have them know Mom is looking at their accounts."