Business Insider/Sam Shead
Skype cofounder Niklas Zennström on stage with Second Home cofounder Rohan Silva.
Speaking at the Second Home startup space, Zennström said: "[Running a business is] a lot of pressure for different reasons. You're going to run out of cash. How do you deal with that? And maybe your team is like 'are we going to be able to make it?'"
The billionaire, who founded file-sharing site Kazaa prior to Skype, added: "As the founder, you cannot blink. You need to always be very confident it's going to be fine, even if you're panicking. You need to be like a duck in a pond. Calm on the surface but maybe paddling underneath the water."
Zennström, reported to have a net worth of $1.3 billion (£890 million), said he's been fortunate enough to receive a lot of support from his wife during his career and told other founders that they need to talk to their own families and explain that they might not be able to go on vacation for a while.
He also advised founders in the audience to hire the best people possible: "You need to recruit people that are smarter and better than yourselves ... never compromise on quality."
Over the last 10 years, the Swede has been investing in promising startups worldwide through Atomico - a venture capital company he set up in London after selling Skype to eBay for $2.6 billion (£1.8 billion). The fund has backed the likes of music streaming service Last.fm, "Angry Birds" creator Rovio, and taxi app Hailo.