Jessica Alba used to feel ''like an impostor.''

The 34-year-old actress, whose eco-friendly brand The Honest Company is valued at $1.7 billion, claims she never thought she was ''smart'' until she had her daughters, Honor, seven, and Haven, four, with husband Cash Warren.

The 'Sin City' star said: ''For a long time, I didn't think I was smart. I felt like an impostor. It's not until you feel whole in yourself that you fit in anywhere. And it took me becoming a mom to actually feel that way.''

Despite her doubts, Jessica has always been business savvy.

She told the October issue of SELF magazine: ''I've always been business-minded. I approached Hollywood like a business. I was very calculated. I wanted to be treated like a guy; I wanted to put asses in seats. I saved my money, invested wisely and marketed myself. I've been building my own personal brand over time.''

The brunette beauty credits her parents for helping her to develop thick skin when she was a ''chubby'' child and battling asthma.

She explained: ''I was on a swim team, and I was chubby and slow and dead last - a full two laps last. I was crying and couldn't breathe.

''My mom and dad were like, 'You started this, you're going to finish it!' My parents made me stick to stuff, pick myself up. It's painful to go through, but I appreciate that tough love.''