The 35-year-old actress, who has eight-year-old daughter Suri with ex-husband Tom Cruise, claims she never believed she could carve out a career in Hollywood while growing up in Toledo, Ohio.
She said: "Growing up in Ohio, I thought being an actor was something that could just never, ever happen. If I could go back, I'd tell that girl to just relax! It's only a plane ride away."
And Katie admits she's trying to have the same laid back attitude when it comes to be a working single mother.
She told PEOPLE magazine: "You do the best you can. Some days you feel really good about yourself and some days you don't. Motherhood has taught me to just let go of some things, to relinquish control."
The former 'Dawson's Creek' star also insists she no longer cares what people think about her.
She said: "I really just don't care. A lot of good things have happened to me, so I focus on that, and the other things that get focused on by the press or whoever - I'm just not interested."
But Katie is eager to fall in love again, despite having a failed marriage under her belt.
She added: "I'm a very loving person. Of course I'm open to finding love again.
"What I've come to understand is that your dreams will happen, but they might not happen when you want them to. There are some things you just have to wait for."