Virgin founder Sir Richard Branson's got a well-earned reputation for being the sort of swashbuckling character who never shies away from a risk. Which might lead you to think he'd advise would-be entrepreneurs to jump into new ventures with both feet, quitting their day jobs and going all in on their dreams.

But on his blog recently he actually said the opposite. You may have heard that a slow and steady approach is fatal to startups, but Branson reveals it worked for him (twice), and argues that keeping your day job is actually a better choice for most entrepreneurs.

Both Virgin Records and Virgin Atlantic started as side hustles  

A lot of would-be founders have heard the message, popularized by the likes of Y Combinator founder Paul Graham, that to succeed with a startup, you have to go all in. "The number one thing not to do is other things," Graham has advised entrepreneurs. "Don't go to graduate school, and don't start other projects. Distraction is fatal to startups." 

This all-or-nothing attitude is at the heart of startup mythology, but it clashes with reality for a lot of would-be founders. "The biggest barrier for many people starting a business often isn't access to resources, support, or mentoring. It's simply not being able to quit their day job," Branson writes. So are your startup dreams doomed to fail if you keep your job?

Nope, answers Branson. And he would know. Both Virgin Records and Virgin Atlantic started as side hustles.

"Some of the world's most successful companies began as side projects, with their founders working evenings or weekends to turn their ideas into realities. Virgin is a prime example of this -- all of our Virgin businesses started while we were working on something else," Branson reports. "Virgin Records was originally a side project as part of Student magazine," while Virgin Atlantic started "as a side project while we were running Virgin Records."

One person's distraction is another's breathing room

Keeping your day job might be a distraction from the sort of maniacal commitment Graham celebrates, but Branson sensibly points out it also lowers the downsides of starting a business and therefore the burden of stress on the founders. Not being mad with anxiety about money has big upsides.

"We've found that those who apply and plan to grow their idea while still working their day jobs are more confident in their ability to manage their money and time. Not having to be reliant on their new business to provide them with a full-time income, they are given a bit of breathing space and time for their idea to gain traction," says Branson of a startup loan scheme he's involved in.

Science backs him up on the benefits of starting your business as a side project. One study comparing "hybrid entrepreneurs" (a fancy term for those who keep their day jobs at the beginning) to all-in entrepreneurs found that businesses started by hybrid entrepreneurs were actually 33 percent more likely to survive. And as the example of Virgin Atlantic (as well as eBay and Apple, which were started while at least one co-founder was moonlighting) proves, this isn't just true of mom-and-pop businesses.

The bottom line is that "go big or go home" advice makes for compelling mythology, but both hard evidence and the experience of no less than Richard Branson suggest keeping your day job isn't a fatal mistake for most entrepreneurs. In fact, it's more likely that Graham's obsessive approach kills more businesses than it saves by spooking would-be entrepreneurs off giving their dream a go.

And, as Branson points out, "if you have an idea for a business that is keeping you up at night, it would be such a shame to waste it." So go ahead and get started even if you can't afford to quit yet. Some in the startup world will sniff at your efforts, but not the Virgin boss.