Penelope Cruz has "become an expert at hiding" her fears.
The 39-year-old actress often feels threatened by "crazy" things, which trigger anxiety and agitation, but she's been suffering with phobias for so long she's learnt how to conceal them.
She said: "I have so many fears. I have become an expert at hiding them but I am so full of them. I'm not giving you examples because they are all so crazy.
"Everybody thinks I'm so centered and relaxed but it's so opposite to what goes on inside me. But I've been working on it all my life, so it gets better."
'The Counsellor' star now has to deal with the pressures of motherhood since welcoming her children, two-year-old son Leonardo and five-month-old daughter Luna, into the world with her husband Javier Bardem.
However, despite only getting "not even three" hours sleep a night, the brunette beauty insists the joy she gets from being a mother makes it all worthwhile.
She explained: "I don't mind. It fills you so much it doesn't matter that you're always exhausted. It gives you so much happiness. You want to enjoy every second."
Meanwhile, Penelope - who married Javier in July 2010 - decided to cut back on the amount of time she was spending on film sets six years ago in order to start a family and raise her children herself.
Speaking to the Daily Mirror newspaper, she said: "I was going from set to set.
"I was never in my house and I didn't have a life ... You need to have time for your own life and as a mother that changes even more.
"Family is the most important thing for me ... and if you have children you want to raise them yourself."