32-year-old CEO who raised $40 million: These 2 thoughts are holding you back

Melody McCloskey entered the start-up scene as a 26-year-old female entrepreneur trying to build an online platform in the beauty industry.

She had no software engineering background, was not part of an accelerator program, and had few mentors.

The odds were stacked against her, and she knew it.

"I was in an industry where it's mostly people who don't look like me building companies that aren't like the company I'm building," McCloskey told CNBC.

Within five years, McCloskey co-founded StyleSeat, an on-demand beauty appointment booking company. StyleSeat has raised $40 million in venture capital funding and has done $3.2 billion in cumulative sales.

"In the beginning I was definitely overwhelmed with all of the reasons why I shouldn't do it," she said. Here are the two main thoughts she had to ditch to become successful.

If you want to start a side project or start a company, you have to change the way you think, McCloskey said.

"Everyone can think of a million reasons why you shouldn't do it," she said. "'I don't have the time,' or 'I'm not smart enough' or 'I haven't done this before.'"

"The reality is, no one has done it until they do it," she said.

Though McCloskey is a notable entrepreneur in Silicon Valley today, her path to get there was not a straight line. Before starting StyleSeat, she worked in media as a manager for Current TV. In high school, she actually felt discouraged from entering the tech world after being the only female in an advanced computer science class. But she worked through the self-doubt and went for it.

"Few people have the capital until they just get something going," McCloskey said.

"Fundraising is a challenging process," she added. "You've failed at it until you've succeeded. It's the type of process where you'll get 40 'nos' and then you will get a handful of 'yeses' in the best case scenario."

To avoid getting bogged down with all the negative responses, she had to actively motivate herself.

"You just have to wake up and say, 'I'm going to learn from past meetings, past conversations. And I'm going to get smarter and better and I'm going to kill it in these next meetings,'" she said.

"I think that everyone should do what they love and not be fearful of all of the reasons why they shouldn't," she said.