Want a brilliant side hustle or business idea? Stop waiting for a 'lightbulb moment,' experts say

A great business idea will never strike you like a lightning bolt out of the blue.

That's according to Catalina Daniels and James Sherman, the authors of "Smart Startups: What Every Entrepreneur Needs to Know — Advice from 18 Harvard Business School Founders." They wrote the book after interviewing 18 HBS graduates who launched notable startups like Rent the Runway and Blue Apron.

One of their top takeaways: There's no such thing as a "lightbulb moment," where a fully-formed idea for a successful business suddenly pops into your head.

"There is this myth that as an entrepreneur, you should have a lightbulb moment: You wake up one day [and] see the light: 'This is an idea worth pursuing.' You go after it, you raise funds, you become successful, blah blah blah. Well, our interviews entirely busted that myth," Daniels tells CNBC Make It.

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Daniels and Sherman, both venture investors, are also Harvard University alumni who've founded businesses. The "lightbulb moment" concept ignores the time and work it often takes to flesh out a successful business idea, they say.

"A lot of aspiring entrepreneurs have this romantic view that that's going to happen to them one day, or that it needs to happen," says Daniels. "Well, it didn't happen with [any of] the entrepreneurs we talked to."

Around half of the entrepreneurs interviewed for the book "had no idea to start with," Daniels says. They just knew they wanted to create something.

Josh Hix and Nick Taranto, co-founders of meal kit startup Plated, used a "deliberate ideation" process to find their concept, says Daniels. That meant spending "six months, full-time, looking at hundreds of ideas before they landed the idea for Plated."

In the deliberate ideation process, "you search for things that are interesting, trends, things you're passionate about, whatever — but no lightbulb moment," Daniels says.

Other founders used what Sherman and Daniels call an "organic ideation" process, where they slowly realized they could build businesses around trends or problems in their own day-to-day lives.

"At some point in time in their lives, with hindsight, they can connect all the dots and basically come to an idea that is worth pursuing," says Daniels.

She cites Gil Addo, the CEO and co-founder of virtual health care startup RubiconMD, whose grandmother had to repeatedly travel from Barbados to the U.S. for follow-up visits after having brain surgery.

Years later, while studying in India, Addo saw the potential for cost savings with virtual medical consultations, Daniels says. But he was only able to fully flesh out his business idea, drawing on his childhood, after picking up industry experience working for a health care consulting firm.

"You're always going to go two steps forward, a step back, a step forward, maybe two steps back," says Sherman. "It's a process, moving the business ahead in a positive way, but it's definitely not linear."

Once you develop an idea, test its viability by using what Sherman calls an "ideation triangle." Judge it based on three key criteria:

1. The size of the opportunity: How big is the market? Thoroughly research the type of business you want to launch and the market you'll enter, and talk to potential customers or clients for valuable feedback.
2. Relevant skills: "It's not a requirement that you have direct industry expertise. What is a requirement, though, is that you have relevant skills to pull this off," Sherman says. You should also be thoughtful about bringing on co-founders or employees to fill in any important skill gaps.
3. Passion: It sounds simple, but if you aren't passionate about your own business idea, why would your customers or investors be?

"That is going to be a motivator and carry you forward in the business with the ups and downs, the emotional highs and lows," says Sherman. "That passion is absolutely essential. You need to radiate that passion as [you are] selling to customers, hiring [employees], selling to investors."

Lastly, accept that your odds of failure are probably somewhat high — and be willing to proceed anyway. You have to be someone who "understands the risks, and is willing to go for it," says Daniels

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