Leaving any role is a daunting task, especially when the company you work for is an industry giant.
But that was the exact situation advertising firm M&C Saatchi's current worldwide chief executive, Moray MacLennan was in over 20 years ago.
In 1995, when the Saatchi brothers left the advertising agency they had founded in 1970, Saatchi & Saatchi, MacLennan had a choice to make - stay as the managing director with the company he had been with since graduating college, or move on with the brothers to start a new agency?
"I walked out, I remember saying to my secretary, 'I'm going out now.' She said, 'how long are you going to be?' and I said I'm going to be a long time. And I walked out and never looked back."
Now MacLennan stands as the worldwide CEO of M&C Saatchi, the company he later formed with the brothers, and now one of the biggest advertising agencies in the world.
Describing the experience as a "fork in the road" to CNBC in an episode of Life Hacks Live, MacLennan doesn't regret his decisiveness.
"Sometimes you need to be decisive in life. No question you need to make a decision. You need to make it quickly or sometimes you do need to ponder. It was a difficult one."
"My advice I suppose would be if you're in a real quandary like that? Go with your heart."
"You may end up being wrong. But at least you'll end up going wrongdoing something that you're passionate about," added MacLennan.
In the first days of M&C Saatchi, MacLennan and his team worked out of an apartment, growing their business one client at a time.
"What I've learned about starting businesses, largely watching other people start businesses, is that it takes longer than they think, I always put their business plans a year back because they're optimists, but you've got to be optimistic."
"You start a business thinking it's going to work. You don't think it's going to fail and it doesn't usually happen as quickly as you think it's going to happen. So it takes a little bit longer and it's hard work," said MacLennan.
Having learnt some major career and life lessons from the experience, MacLennan is urging fellow start-up professionals to be one thing - passionate.
"You've got to enjoy it. So you've got to do something you want to enjoy. Expect it to be really hard work. It'll take up weekends, you'll be away from your family if you have one and you've got to give everything to it."
"It's stressful but boy it's worth it because you've got freedom, you've got freedom and responsibility. You can never turn around and say well the problem is 'they'. You're they; 'They didn't sell', it's you and it's your decision. So that's the fantastic liberating feeling about doing it," MacLennan added.
Life Hacks Live is a series produced by CNBC International for Facebook, where tomorrow's leaders get to ask some of the world's biggest influencers for advice. You can watch the full episode here.