Kara Goldin broke her Diet Coke habit by making her water "less boring" by putting fruit in it. It was the ‘aha’ moment that lost her 50 unwanted pounds and built a $100m company destined to be a $1bn unicorn. Kara is founder and CEO of hint®, a healthy lifestyle brand that produces unsweetened water, and now a sunscreen spray without harmful oxybenzone and parabens. Melinda Wittstock talks to Goldin about what inspires and frustrates her as a female entrepreneur, why no one really knows what they are doing (even if they look like they do), and why the biggest obstacle to success are the walls we architect for ourselves.