Top 3 common mistakes to avoid when starting a side hustle, based on my experience making $142,000/mo from Amazon alone.

In 2018, I was a full-time graduate student and a part-time course designer at my university. Driven by a class project and my own personal challenges, I decided to start a side business selling card games on Amazon to help individuals develop "human skills" such as emotional intelligence and critical thinking.

My side hustle sustained me throughout my Ph.D. journey, and now I have five sources of income. Initially, I had little knowledge of managing a business, but now I am proficient in it.

I am a speaker, EQ instructor, and university lecturer who also offers freelance business consulting and sells Mind Brain Emotion card games through my website and Amazon. My Amazon business generates $142,000 in monthly revenue.

I always advise aspiring entrepreneurs on how to create side hustles that align with their schedules and lifestyles, and to avoid these three common mistakes.

DON'T MISS: The ultimate guide to earning passive income online

1. Don't overcomplicate your product

Initially, I experienced imposter syndrome when I began my side hustle. To alleviate this self-doubt, I invested a significant amount of time in researching and creating innovative product features that I believed would impress people, such as integrating augmented reality components into the cards. However, this strategy ultimately proved counterproductive, as it perplexed my users, increased my workload, and complicated my existing offerings.

After launching multiple products and listening to numerous entrepreneur pitches, my top advice is to avoid overcomplicating your business. Doing so will not only hinder your progress but also increase your expenses.

The secret to achieving success lies not in adding more features, but in comprehending the fundamental worth of your brand.

So before you begin any side hustle, ask yourself two key questions:

1. What is the fundamental need that my product or service fulfills?
2. What's the smallest number of steps I can take to get there?

By using real-world feedback, you can iterate and evolve your solution based on actual customer needs, rather than assumptions and second guesses. This can be a refreshing change in a world where there are many options to choose from.

2. Don't settle for subpar service—even if you're on a budget

Collaborating with fellow side hustlers who share your sensibility can be a great way to save money and grow your business. However, it's important to be aware of the potential risks of working with a collaborator who is constantly growing and changing, which can lead to unpredictable service.

I parted ways with a social media manager and SEO vendor who were both solo entrepreneurs and wanted to expand their side gigs into agencies. In doing so, they handed my business to inexperienced hires who lacked knowledge of my industry.

Although I believe in giving people the opportunity to learn and enhance, I wasn't receiving the attention and priority that I was assured.

Despite being unhappy with the service and incurring additional costs, I continued to use the same SEO vendor for an extended period. As a result, my earnings for the year were negatively impacted, with November, traditionally my most profitable month, experiencing a 55% decline compared to my best month in 2023.

While working with others can bring advantages, it's essential to exercise caution when selecting employees. If you sense that something is no longer beneficial, don't hesitate to make a change.

3. Don't just rely on networking to move your idea forward

I yearned for clear roadmaps, blueprints, and decisions as a solo entrepreneur, so I applied and was accepted to incubators at Harvard, UC Irvine, and USC.

I had access to top executives and advisers, but these meetings often left me feeling confused and overwhelmed. Despite their good intentions, many of these advisers ended up projecting their own ambitions and mistakes onto me.

I suggest being cautious of skepticism and feedback in meetings, but avoid being influenced by the opinions expressed. I've discovered that over-relying on external validation can cloud my judgment and impede my progress.

While a veteran perspective can be valuable, it's ultimately up to you to take action and make your own decisions. It's important to trust your own instincts and remember that this is your journey.

Dr. Jenny Woo is a Harvard-trained educator, EQ researcher, and founder and CEO of Mind Brain Emotion. She developed a series of educational card games and mental health tools to help kids and adults develop human skills in the age of AI. Her award-winning card games, the 52 Essential Relationship Skills, 52 Essential Coping Skills, and 52 Essential Interview Skills are used in 50+ countries. Follow her on Instagram, LinkedIn, and YouTube.

Sign up for CNBC's online course on earning passive income online to discover common streams, tips for starting, and real-life success stories. Save 50% with discount code EARLYBIRD.

Sign up for CNBC Make It's newsletter to receive tips and tricks for success at work, with money and in life.