What money lesson do you wish you’d learned before starting a business?

Starting a business involves plenty of learning, but which money lesson do you wish someone had explained before you began?

For example, was it understanding the difference between sales and profit, planning for quieter months, or noticing how quickly small recurring expenses add up?

I run Finance Nest Blog, where my aim is to make everyday money topics easier to understand through clear explanations and practical examples. Business finances are a topic I’d like to explore more, especially the questions people face when they’re just getting started.

What’s one financial mistake you learned from, and what do you do differently now? Experiences from freelancers and side-business owners would be welcome too.